In Response
Cracking the Playfair
by Pratap Singh
One of the competitions that many Perse students look forward to during the Michaelmas
term every year is the National Cipher Challenge. Organised by the mathematics
department of the University of Southampton, it consists of eight challenges released every
week or every other week; each challenge consists of two pieces of text encrypted in an
unknown cipher. Competitors prepare programs or other strategies in anticipation and when
the challenge is released, try to decrypt the ciphertext as fast and as accurately as possible.
The early ciphers are usually quite straightforward to identify and break, but they get harder
as the competition goes on. The hardest challenge is the very last, challenge 8B, which is
often a variant on a complex classical cipher. Past ciphers used for challenge 8B have
included the ADFGVX and the Trifid. In 2013 it was a variant of the Playfair cipher.
Devised in 1854 by Charles Wheatstone, the Playfair cipher puts the alphabet
into a 5x5 grid, with ‘I’ and ‘J’ usually occupying the same square. The precise
arrangement of letters in the grid is the secret key of the cipher. An example
key is shown at right:
T
S
F
M
V
H
A
G
N
W
E
B
I
O
X
Encryption is done by first splitting the text into pairs of consecutive letters,
then forming a rectangle in the key grid with the two letters of each pair as the
corners. Each letter is then replaced by the letter in the horizontally adjacent corner in this
rectangle. If the two letters are in the same row or column, each letter is replaced by the
letter to its right or below it, respectively, wrapping around if this goes over the edge of the
key. If the two letters are the same, the second is replaced by X and then encrypted as
above.
For example, the key above would encrypt ‘QU IF AC IT PE RA LI UM FA CI TP ER SE’ as ‘UM
KG BD FE RP HD FK MN GS BK HR PT BT’.
This cipher was in common use as recently as WWII. Famously, when future US President
John F. Kennedy was stranded in the Solomon Islands after his patrol boat was hit by a
Japanese destroyer, he radioed a message encrypted with the Playfair cipher. The fact that
he was rescued and not captured is in part due to the strength of the Playfair.
The 2013 National Cipher Challenge also had a WWII theme. Over the course of the first
seven challenges a lot of the story and context of the encrypted communications had been
revealed. This meant that I could use an attack based on cribs - small pieces of text such as
names or salutations that I knew were likely to appear at certain locations in the text. A
crib-based method is a very successful and established way of attacking a cipher. It was an
important part of the British attack on the German Enigma cipher during WWII.
Interestingly, one of their most common cribs was ‘Keine besonderen Ereignisse’, meaning
‘nothing to report’.
I wrote a program in Java to try to cryptanalyse the Playfair cipher. The main observation I
used was that any mapping of a pair of ciphertext characters to a pair of characters in the
crib would restrict the number of possible relative arrangements of these four letters from
P
C
K
Q
Y
R
D
L
U
Z
over 12,000 to just 20; and if one of the letters was common between the crib and the
ciphertext pair there would be only 2 arrangements.
My strategy was to combine the information from the mappings of crib pair to ciphertext
pair to try to recover parts of the original key grid. I designed a data structure called a
mapping, which was initialised to store all possible partial key grids that would come from a
single mapping of crib pair to ciphertext pair. The algorithm would then iteratively try to
merge together two mappings which had a letter in common: it would rotate every partial
key grid in both mappings to have the common letter in the top-left corner; it would then
effectively try to place every partial key grid from the first mapping on top of every partial
key grid from the second mapping. If there was a contradiction, i.e. the same letter appears
in two different places or two different letters occupy the same place, that key grid would be
discarded; otherwise it would be included in a new mapping. At the end of this step, the
two original mappings would be deleted.
There were two possible stopping conditions for this algorithm. The failure stopping
condition took place when at any stage a mapping contained no partial key grids. This
meant that one mapping entirely contradicted another, implying that original cribs were
incorrect. The successful stopping condition occurred when all possible merges of mappings
were completed. The algorithm would have found one or several partial key grids that
correctly encrypted all of the crib pairs to ciphertext pairs; it would then use each partial key
grid to decrypt as much of the ciphertext as possible, for examination by hand.
The algorithm ran quickly enough on my computer that I was able to try several different
cribs. If a crib was successful, I would look at the partial decrypts and try to find word
fragments which I would complete and add to the cribs. In this way I was able to reconstruct
the original key.
Although the actual challenge 8B was encrypted with a slight variant on the standard
Playfair, I was able to use this algorithm to crack the cipher and recover the plaintext. I was
fortunate that my time was fast enough that my entry was jointly awarded the 2013 Trinity
College Prize, for being the joint runner-up in the individual competition.
For a detailed description of the algorithm, and to see how to decrypt the following message,
please visit:
http://persestudio.org/2014/05/05/cracking-the-playfair-cipher-pratap-s-year-10/
or scan the QR code.
FAEBABOUQBFSBSNEQLSRWFBIFNIEHYCNWAUPDUSYPVROKBSREBEHQCSBRDNFPQRWPOFG
IAGPLEEFKHRBUDSKBNPOGQLGFBGHSIFDRWPOBSEBENKUFBUPMZLGKBSREBKQQYPQBENE
SFCFQLSWWKTYDSULSIOVFGWARELPSBQLBFQLRIQVFKAQLPNGPRSYAFIEQLQLFEBAQKSR
AQFRPGURFIGPMNESRELYFSKQRMSABTUOHQROLQTDLVPOKBSREBVEREUMGPKPQBEPGPIF
BSAQGPVERERLEFKVQBDETMORKHRLEFKVQBTGDSQLKBSREBSKEXSBFKQLSBBPKHSBFRDK
APMEBTUOREKHQLSBSRPLTAABOUQBNESKDQKQBERMBFSKAQEBRPFSVRHYRDMLQKTAEAFR
FBGKUDFEUPEQSEINGKESREBRMPISBEMLFIERLZLEEFKHDEGPLHTMSKFKQBQYUDSAOUAB
OUQBREXRFSVEREUMGPKPQBSKMABTUOENRESQQKTAEAFRDBGXPOLTTVRDLEEFKHDBAG
Response to Cracking the Playfair by Pratap Singh
Pratap reports on his success in the 2013 National Cipher Challenge competition, and
specifically how he tackled the last and hardest of the challenges presented to contestants
by the University of Southampton. The task was to decrypt a given message, not even
knowing what system had been used for its encryption! The only clue was that it was likely
to be a variant of one of the classical schemes. Moreover, even after guessing that the
Playfair cipher might have been the one which had been used, Pratap’s task had barely
started, since –obviously! – the secret key was secret, making the ciphertext appear to be a
stream of gibberish. Despite this daunting prospect, Pratap succeeded in deciphering the
message. In fact he did vastly more than that: he developed an algorithm, or systematic
method, which could, with a certain amount of intelligent human input as well, work to
decipher any other message using the same system, whatever the secret key. It was his
implementation of this algorithm as a computer program which impressed me most about
Pratap’s achievement, and not just the fact that he successfully deciphered this specific
message.
In his report, Pratap gives a clear description of the Playfair cipher, illustrated by a small
example to show the reader very clearly how it works. He then goes on to describe his
method of attack, using the system of ‘cribs’ which is just the sort of trick used by his famous
predecessors, Alan Turing and his colleagues at Bletchley Park during the Second World War.
The point about a crib is that if you can guess a small part of the message, which is often
possible for the opening greeting for example, this gives you a small set of possibilities to try,
and each one can be used to partially decipher the whole text. Then you begin to see parts
of words, which gives you some ideas for more components of the key, which you can
systematically try out, until the job is done. Of course, all this is a lot harder to carry out in
practice, and effectively impossible without some assistance – such as a computer program!
Pratap’s report contains a quite detailed description also of his program: which data
structures he decided to use, which methods had to be implemented on these, and then the
strategy for the algorithm itself. This description is again illustrated by working through a
genuinely difficult example.
There are many things which impressed me about Pratap’s report. It is very well written as a
piece of exposition: clearly he has had some excellent role models amongst his teachers! He
shows how well he understands the cipher system itself, and what is needed to crack it.
This is an excellent skill to have, one which is currently much in demand. And in addition,
though without making a big fuss about it, he shows that he has the expertise to follow
through the idea with a working computer program. Not only can he ’decode’ very well, he
can also ‘code’ brilliantly!
Prof John Cremona (1974)
University of Warwick
What are the Advantages and Disadvantages of Investing in a 1:1 iPad programme in
Secondary schools?
by Stephanie Budenberg (Y11)
My HPQ project this year was on iPads in schools, and whether they are a beneficial
investment in a learning environment. The education industry has always been extremely
interested in finding ways to improve teacher pedagogy and the students’ ability to learn.
Recently, with the release of the new apple iPad a number of schools have taken to
introducing them in a bid to use the new technology to their gain. My project explored the
different advantages and disadvantages of this investment, to see whether they were a
positive influence or not.
Advantages:
I found that there were a number of advantages with a 1:1 iPad system, such as portability,
ease of access and an increase in collaborative group work; these factors seemed to increase
student enthusiasm to engage. Other advantages of the iPad for students are that it has the
potential to help students become more competent and more responsible with using
technology, consequently allowing them to prepare for a future using and being surrounded
by technology. As Tricia Kelleher said when I interviewed her, the main reason for
introducing iPads into the Stephen Perse Foundation was that ‘we’re living in a digital world,
we have to be a digital school.’
Perhaps the most obvious advantage of the iPad is its potential to unlock individualised
learning and allow for the possibility of a curriculum tailored to the individual’s needs and
capabilities. Software such as Knewton and Khan Academy have revolutionised online
learning and awakened creativity and interest in learning. At the Longfield Academy in Kent,
it was found that over 75% of their students agreed or strongly agreed with the statement
that ‘working with Apps has improved my learning.’
Disadvantages:
There are significant disadvantages that were found with the iPad in relation to its use in an
educational setting. One of these is the fact that they were not originally intended for
educational application. Therefore, the iPad is not designed to last for years, merely to
continue working until the release of the next generation or newest software. This means
that in order to obtain the highest level of functionality from the iPads, the institution needs
to replace them every 3-4 years just to provide a working device. Furthermore the iPad also
has the capability to break easily - especially around children.
The iPad also offers the possibility of distraction in schools, a major issue as it can be very
difficult to tackle. The iPad, as well as offering a wide range of educational Apps, also offers a
wide range of Apps such as games, which are aimed at distracting the mind. Since these are
personal iPads the games and social media Apps are inevitably going to be on the iPads.
Overuse of these Apps was reported in some instances to lead to health issues among the
students, such as stomach cramps, insomnia and developing a narcissistic personality.
Furthermore, this constant ability to access the online world can lead to an increase in cyber
bullying.
Conclusion:
To conclude, although investing in a 1:1 iPad programme offers a large number of both
advantages and disadvantages it seems to me that the advantages outweigh the
disadvantages. However in order to integrate them into schools in the most beneficial way,
one has to make changes to accommodate the iPads, and also ensure that everyone,
students and teachers alike, is competent in their use. If the students and teachers are not
competent in their use then iPads become a tool for distraction, not a tool for education.
What are the Advantages and Disadvantages of Investing in a 1:1 iPad Programme in
Secondary Schools? Stephanie Budenberg
Response to Stephanie Budenberg
Stephanie has brought together an insightful and extremely topical debate about the use of
technology in the classroom. It’s part of a bigger trend relating to the digitisation and
mobilisation of everything. Users, whether they’re students, teachers, business people or
consumers, want complete flexibility to do anything, at anytime and anywhere they
choose. The technology industry is challenged daily to figure out the apparently insatiable
desire for flexibility and everything on demand. Stephanie correctly identifies that the
education use case is quite different: ensuring that tablet devices are used in educational
institutions for their intended purposes and making learning more engaging, fun and
creative whilst avoiding distracting students – is key.
iPads were originally sold as a consumer device, although they were applied to business
before education due to a number of factors: 1) businesses typically have larger budgets; 2)
businesses are more self-sufficient when it comes to app creations, often having in-house
developers or the ability to outsource. The Education sector, for the most part, had to wait
for an ecosystem of iPad developers to become established before it was able to adopt this
technology, since schools and education authorities don’t have resources to commission
bespoke apps.
Stephanie highlights portability, connectivity and use as a learning aid as advantages, with
which I completely agree. Key to being a learning aid is the interactivity that a touch device
provides, making exploration more natural. The iPad can bring subjects to life more and help
students with different learning needs. Animating a biological process, being able to
manipulate a molecule in 3D or watching videos and reconstructions of historical events are
all more engaging than reading words from a static text book.
However, to this day, the iPad and other tablet devices remain largely content consumption
devices. Stephanie correctly highlights apps like Garageband, Popplet and Pages as creative
apps, but they’re few and far between. I was excited to read, just yesterday, about Pocket
Code, a new app that enables the user to write new software apps from the tablet
itself. There have been a number of impressive apps for artists also, but it’s still a minority
of artists that warm to technology, rather than traditional materials, to help them express
themselves. Even typing continues to be difficult using a tablet. Creation is and will
continue to be a core part of education and until there is a broad range of creation apps on
tablets that are more usable than traditional materials, there is still a lot more work to do.
Matt Goodridge (1997), Product Manager, Google
Head, Heart & Soul
Shedding Light on the Newborn Brain
Back in the 1980s – like now – The Perse excelled academically. Unfortunately I did not. I
was not particularly bad – I just was not particularly good either. Average. I scraped into
medical school with 2Bs and a C in Physics (mediocre even back then). I was not quite sure
why I ended up applying for medicine. However, I never really had time to regret it as I was
swept away by university life. In my third year I opted out to study for an intercalated
degree in Physiology. It was while studying for one of the modules on foetal and neonatal
physiology that I saw my first patients in the hospital: and these were like nothing I had ever
seen before. Tiny little lives (some babies weigh little more than 500g) being kept alive by
what seemed like space-age machinery and applied physiology.
Neonatal intensive care is one of the great success stories of twentieth-century medicine –
ever smaller and sicker babies being kept alive through technological advances. However,
the challenge was – and still is – to allow the brain to develop outside the protective
environment of the womb and minimise any further damage. Despite improvements in
neonatal medicine a significant number of children go on to develop life-long
neurodisability.
One of the technologies used to study the newborn brain uses near-infrared light to
measure oxygen in the brain. It fascinated me that by using just laser light you could see
inside the living brain. Working with a team of physicists and engineers at University College
London, I completed a PhD on the development of a unique 3D optical imaging system, the
second generation of which has just been brought up to the Evelyn Perinatal Imaging Centre,
a newborn functional brain imaging unit I run at the Rosie Hospital in Cambridge.
Medicine opened my eyes to the world around me and I have met many truly inspiring
patients, parents, doctors and scientists throughout my career. I have also been extremely
fortunate to be living through a golden age for neuroscience where by applying physics we
have gained unprecedented access into the brain – even very tiny ones.
Clockwise from top:
Studying newborn babies during medical
elective in Nepal.
Measuring cerebral oxygenation on members of
the public during the Cambridge Science Festival
in 2014
Visit to Downing Street to promote the medical
charity Action Medical Research
Harnessing the therapeutic power of DNA to repair damaged hearts
Growing up in Cambridge, few Perseans can have escaped the fact that Cambridge was the
location of the discovery of the molecular structure of DNA – famously termed the ‘molecule
of life’ - by Watson and Crick in 1953. During my biology lessons at The Perse I remember
being introduced to the complexity of DNA, and its fundamental properties as the molecular
‘instruction manual’ for every cell, the building blocks of the tissues and organs of our
bodies.
Building on the foundation laid in my Biology and Organic Chemistry A level classes, I
continued to be fascinated by DNA and its potential to revolutionise medical practice whilst
at medical school in Oxford. Whilst the majority of clinical DNA research in the last few
decades has been focused on the diagnostic potential to understand the genetic component
to all diseases affecting human health, known as ‘genomics’, I became interested in the less
prominent field of gene therapy, where we aim to harness the therapeutic power of DNA
for medical benefit. During clinical school at Oxford University I studied the emergence of
the field of gene therapy for cancer in the late 1980s and early 1990s, not realising at the
time that this would lay a critical foundation for my future career.
After Oxford I moved to London and started my training in cardiology, a specialty fuelled by
mechanical technology advances in the last 30 years, with coronary stents, complex
pacemakers and defibrillators, electrical ablation technology and modern imaging
dominating the training curriculum. However, I held onto a vision that biological repair
would be the future, and I was very fortunate when in 2004 Professor Philip Poole-Wilson
and Sian Harding invited me to study for a PhD thesis with them in the cardiac research
laboratories of the National Heart and Lung Institute at the Royal Brompton Hospital and
Imperial College. Here serendipity intervened, as initially the proposal was a thesis in cardiac
stem cell research, but when I arrived there was a problem with the stem cells being
produced by the lab at that time. Sian and Philip suggested I start using a new gene therapy
virus they had in the lab, and 3 years later, my research thesis was focussed entirely on
cardiac gene therapy.
The medical condition we are aiming to treat is known as ‘heart failure’. Heart failure can
have many different causes where the common feature is a significant degree of damage or
dysfunction of the heart muscle, the myocardium, which causes weakening of the muscle
used to pump blood around the body. With increasing survival rates following heart attacks,
cancer treatments using cardiotoxic chemotherapy, the epidemic of obesity and diabetes,
and the ageing population, all factors which can cause damage and weakening of heart
function, heart failure is becoming a major health problem in modern society. It is estimated
that between 0.75-1.0 million people in the UK are living with heart failure, and it is a very
malignant disease, with survival rates unfortunately similar to some of the worse cancers
despite current treatments.
Laboratory research at Imperial College and other universities around the world has
characterised the biology of the failing heart in exquisite detail over the last 30 years. We
and others have identified a critical gene for normal heart muscle function which is
progressively switched off in the damaged heart, driving the progression of heart muscle
dysfunction, analogous to muscle fatigue. The gene is known as SERCA2a, and regulates the
cycling of calcium ions which are responsible for heart muscle contraction and relaxation
during every heartbeat. Calcium in heart muscle cells is like the ‘conductor of the molecular
orchestra’ and when it is disturbed, this leads to many adverse molecular changes which
cumulatively result in heart muscle dysfunction and heart failure, irrespective of the initial
trigger. We demonstrated in laboratory studies that restoring normal levels of SERCA2a gene
expression in diseased heart muscle cells isolated from failing human hearts improved their
function back to normal, at least in the Petri dish. Many further laboratory studies by
ourselves and our collaborators in the US continued, and after crossing many scientific, legal,
administrative and regulatory hurdles, we were finally at a point where we could start to
test the safety and efficacy of SERCA2a gene therapy in people with heart failure.
We use a naturally occurring virus to deliver the treatment gene, and again further good
fortune catalysed our progress. It has been a real challenge to effectively deliver DNA into
heart muscle using conventional viruses in the gene therapy field, and most are based on
disease-causing viruses such as those which can cause colds, the flu and HIV. However, in
cardiology by far the most efficient virus to deliver DNA to heart muscle is a benign virus,
known as AAV, which causes no known human disease. We could exploit this virus, removing
its genes and replacing them with our treatment SERCA2a gene. We then use the modified
therapeutic virus as a molecular courier to deliver our package, the DNA of the SERCA2a
gene, to the failing heart muscle, aiming to restore SERCA2a protein levels, normalise the
calcium, and thereby the heart muscle function.
In 2013, 60 years after the initial description of the genetic code by Watson and Crick, we
delivered the first dose of gene therapy to a heart failure patient in the UK at the Royal
Brompton Hospital in London where I work as a Senior lecturer and honorary consultant
cardiologist. This was part of an international gene therapy trial to assess the safety and
benefits of using SERCA2a gene therapy, delivered by the AAV virus, to people with severe
heart failure where their life expectancy is limited despite modern treatment. At the time of
writing we have now delivered treatment infusions to 14 people in the UK with advanced
heart failure, and are the leading European centre. We are also running a second trial at
Harefield and Papworth hospitals, where we are treating people with mechanical heart
pumps with the same SERCA2a gene therapy. A unique aspect of this trial is that we will take
a small biopsy sample of the heart muscle 6 months after the infusion, and measure if our
treatment gene is present and improving the biology of the failing heart muscle at the
molecular level. To paraphrase the famous advertising quote, this trial will determine if our
gene therapy does ‘exactly what it says on the tin’ – delivering therapeutic DNA to the
human heart.
It is still early days in the development of this novel gene therapy treatment, but I believe we
are now embarking on a new era for the biological repair of the damaged heart in the clinic.
It has been an exciting time and a privilege for those of us involved on this journey, and from
a personal perspective, the seeds for my involvement were sown during my Biology and
Chemistry classes at The Perse.
Dr. Alexander Lyon (1992)
BHF Senior Lecturer and Honorary Consultant Cardiologist
Royal Brompton Hospital
Dr Alex Lyon (left) at the unveiling of the Crick Memorial at Gonville & Caius College,
Cambridge. Dr James Watson, who shared the 1962 Nobel Prize for Medicine with Francis
Crick, signed a school textbook on the structure of DNA belonging to Alex.
Soul and a career in medicine
The nurture of my soul began at The Perse. In April 1943 I went as a boarder to Hillel House,
a Jewish house for about thirty boys who attended school Mondays to Fridays but did not go
to school on Saturdays, the Jewish Sabbath. Hillel House closed in the summer of 1948 and I
went into digs in Cambridge for the last year of my schooling, leaving in December 1949.
My religion did not provide and indeed has never provided me with any spiritual uplift.
Instead I was inspired by the literature, especially the poetry and drama, to which I was
exposed at The Perse. I still remember much of the poetry I learned at school. In the school
production of Hamlet directed by John Tanfield, a History teacher with a great love of the
theatre, I played Gertrude, Hamlet’s mother. Hamlet was played by Peter Hall, later to
become Britain’s leading theatre director. It was a memorable experience.
On the basis of my Higher School Certificate results in arts subjects I was awarded a place to
read Law at Caius College, Cambridge, but it was felt I was too young to go. So I went for two
terms to the Sorbonne in Paris for a soul-enhancing course run for foreigners in French
civilisation. While there I became fascinated by philosophical and psychological problems of
the interaction between mind and body. I decided to abandon the idea of a career in law
and study to become a doctor so that I could be a psychiatrist.
Problem! I had been hopeless at science at The Perse. In order to pursue medical studies I
had to pass examinations in Physics, Chemistry and Biology. I went to Luton Technical
College for a year and just managed to do well enough to persuade Caius to agree to take
me for medicine provided I did my National Service first. So, after two years in the Royal Air
Force I entered Caius to study for a Natural Sciences degree – Anatomy, Physiology and
Biochemistry. While The Perse had nurtured my soul, studying science at Cambridge was a
soul-destroying experience. I had no aptitude for the subject. Having to learn stuff I found
profoundly boring was depressing beyond description. Luckily, in my last year I was able to
act in some undergraduate productions.
After three years at medical school in London and two years in hospital medicine I was at
last able to train to be a psychiatrist and then a child and adolescent psychiatrist. It has been
a wonderful career and twenty years after retirement I continue to write in my field. It was
possible to combine research and teaching with clinical work with disturbed children and
their families. The problems of mind-body interaction or, as our forefathers would have put
it, the location of the soul, that fascinated me when I was seventeen years old, has turned
out to provide the most important challenges for both philosophers and psychologists. I was
lucky – so was my soul!
Philip Graham (1949)
Emeritus Professor of Child Psychiatry
Institute of Child Health, London
Obituaries
Richard Crabtree, 1952 – 2014
Over 250 alumni, friends and colleagues gathered in the School Hall to celebrate the life of
Richard Crabtree, Perse teacher, Scout master, expedition leader and so much more, who
died at the age of 62.
Long-serving colleague Adrian Roberts said: ‘For all of us, Richard’s death was a heavy blow
and his passing, coupled with that of Hugh Vodden only last year, has left a huge gap in the
ranks of Perse staff.
‘His pupils and his colleagues respected his learning and his belief in traditional academic
virtues of careful research and coherent writing,’ he said. ‘As a colleague, there was so much
to like and admire about Richard: his overwhelming energy and drive, his gift for repartee
and his happiness when he saw other colleagues fulfilled and successful. When he walked
into the Common Room you looked forward to his one-liners and throw away comments.’
Richard’s friend since boyhood, Mr Neil Davey QC, said, ‘When in 1971 he went up to St
John’s College, Cambridge he went already equipped with many of the characteristics that
we came to recognise so well and to admire – immense organisational ability underpinned
by relentless hard work; the time-management skills with which to multi-task effectively;
enjoying the company of others; enjoying the process of discussion and persuasion; selfconfidence in taking the lead role; and a positive pleasure in doing things differently.’
Richard led generations of young Perseans from camps in the UK to expeditions in Africa,
Iceland and the Alps, carrying out charitable projects as they went. In 1999 he organised and
led a six-week expedition to East Africa on behalf of the British Schools Exploring Society for
more than 50 teenagers.
The Perse was delighted to be inundated with heartfelt tributes from OPs who felt their lives
had truly been changed for the better through Richard’s teaching and particularly his work
with Scouts.
Here is a just a flavour of them:
The effect of having Richard Crabtree bounce into our lives was a bit like turning on the fun
tap ... He was at the centre of a whirlwind of action. He was a man on a mission with a bold
vision: to run the Scout group to professional standards; even though everyone was a
volunteer. Oliver Metherell (1993)
Richard was an inspiring leader of the Scout Troop during my time at The Perse. He was
dedicated, principled and enthusiastic, but only in hindsight do I realise just how much of his
free time he must have put into all those evenings and camps. Andrew McLeod (1978)
I have been greatly saddened by the loss of Richard, who has been a major influence on the
developing lives of many young people, and extended their horizons, either in
mountaineering, or foreign travel, or as a teacher. For my own part I will be eternally
grateful to him. Steve Charles (1977)
My words about Richard are very simple: he was the first person in my life who truly
understood me. He cared deeply about each of us. Yes, he was my teacher and my Venture
Scout leader - but most of all, he was my dear and trusted friend. Rob Dersley (1998)
Of the thousands of days of my childhood, it is those spent having adventures that I
remember most vividly giving me pleasure and knowledge. At the forefront of all these
activities were Richard's leadership, enthusiasm and empathy. Nick ‘Spike’ Williams (1988)
Mr Crabtree was a truly inspirational teacher and I used to look forward to his lessons with
great excitement … He taught me so much both in the classroom and outside. Nick Wells
(2004)
He gave us confidence to experience the outdoors, learn new skills, to look out for each
other, and gave us much responsibility at a young age. Scouts, under Richard's stewardship,
was one of the best things I ever did. Richard gave an extraordinary amount of his time and
energy over the years to others. His legacy is one of many childhoods immeasurably
enhanced. Rob Minto (1993)
Donald Macpherson (1977)
Remembered by Ranjit Bolt (1977)
Donald Macpherson was the best, the staunchest friend I ever had. He was also one of
the most exuberant and positive people I have known. For these reasons, it was not
merely his passing, so prematurely, but also the manner of it, that so deeply saddened
me. For weeks after I heard the awful news of Mac’s death, he would be the first thought
that came into my mind when I woke up. We were close friends throughout our time at
The Perse. Without Mac (and I dare say the same was true in the other way round) my
life at the school would have been very different, and much harder. Apart from the traits
I have already alluded to, he was also blessed with a great sense of humour. I can still
hear, for instance, in my mind’s ear, some of the hilarious impressions he used to do, not
least of the Headmaster.
After leaving The Perse, and then Oxford, we of course stayed in touch. When I was
going through a very difficult time financially, he twice helped me out, once with a
sizeable loan, once with a gift. Despite the fact that we weren’t seeing nearly so much of
each other as in the old days (he moved up to Scotland on leaving Oxford, to take up a
job with British Rail) he remembered and valued our friendship, and stayed loyal to it.
That was typical of the man – as I say – staunch, true, generous - a person of immense
integrity.
One of the last conversations I had with Mac was in the spring of this year. He had called
me from the hills around Perth, where he was on one of his regular long walks. He had
come to a memorial to one of the Gray girls - the famous Perth family, one of whom,
Effie, married the painter John Everett Millais - and wanted to tell me about it, and them.
He was talking about this famous aspect of local history with such enthusiasm – sounded
so full of life – I still find it almost impossible to believe that, only a few weeks later, he
would be gone. I miss him hugely, and I know that he will remain in my thoughts for the
rest of my days.
‘Sandy’ Green (1942)
James Alexander ‘Sandy’ Green (1942)
Sandy Green joined The Perse in 1935 when his father Frederick was appointed Drapers
Professor of French at the University of Cambridge. His favourite subject at school was
chemistry but by the time he arrived at the University of St Andrews at just 16 years of age
he had decided that mathematics was his true vocation.
After two years as an undergraduate he put his university career on hold when he went to
Bletchley Park to undertake war work.
He later wrote ‘... I arrived in August 1944, and the war in Europe was in its final phase. By
that time M H A Newman's plan to use specially designed electronic computers to assist in
the decipherment of the "Fish" series of coded messages was well advanced. I was one of a
number of new recruits to Newman's section (which was called the Newmanry), and our
main task was to operate these "Colossus" computers, using well-established routines.’
It was at Bletchley Park that Green met his future wife Margaret, a Wren. In 1946 he
returned to St Andrews to complete his first degree. He was awarded a PhD from Cambridge
in 1951. (Sandy's brother Christopher Green (1947) graduated with a BSc in Applied
Mathematics from St Andrews the same year.)
His first lecturing post (1950) was at Manchester University, where Newman was his Head of
Department. In 1964 he became a Reader at the University of Sussex and in 1965 was
appointed as a Professor at the newly formed Mathematics Institute at Warwick University,
where he led the algebra group. He worked as a visiting academic at Princeton and in
France, Germany and Portugal. After retiring from Warwick he became a member of the
faculty and Professor Emeritus at the Mathematics Institute of the University of Oxford, in
whose meetings he participated actively. His final publication was produced at the age of 80.
Green found all the characters of general linear groups over finite fields (Green 1955) and
invented the Green correspondence in modular representation theory. ‘Green functions’ in
the representation theory of groups of Lie type and ‘Green's relations’ in the area of
semigroups are named after him. His final publication (2007) was a revised and augmented
edition of his 1980 work, Polynomial Representations of GL(n).
He was elected to the Royal Society of Edinburgh in 1968 and the Royal Society in 1987 and
was awarded two London Mathematical Society prizes: Senior Berwick Prize in 1984 and the
de Morgan Medal in 2001.
Harry C. Davis (1944)
Harry Clayton Davis (1944)
Dr Katerina Krikos-Davis writes:
Harry Clayton Davis was born in Beccles, Suffolk, in 1927. Following his father's appointment
as Manager of the local Midland Bank, the family moved to Cambridge in January 1936 and
Harry joined the Perse Preparatory. He left the Upper School in 1944, entering Trinity
College, Cambridge to read English in January 1945. A year later, he was called up for
National Service in the Royal Navy and was only able to return to University for the
Michaelmas Term of 1948, graduating in 1951.
After a short period of schoolteaching, Harry travelled to Italy intending to spend three
months in Rome, but, falling under her spell, he stayed for fourteen years! He turned his
hand to many things: broadcaster of news in English for Italian Radio and TV, professional
translator, head of English Language courses at the Italian Middle and Far East Institute
(IsMEO) and teacher of English at Rome University; he also took a second degree, with First
class honours, in Italian Language and Literature, as an external student at London
University.
In 1966 he was appointed to a lectureship in the Italian Department at Birmingham
University, heading the department from 1989 until his retirement in 1994.
Harry co-edited Essays in Honour of John Humphreys Whitfield (London 1975) and published
some good scholarly articles. Teaching, however, was his true vocation and he excelled at it.
On the news of his death messages poured in from past students, including graduates of
forty-odd years, some even travelling to Birmingham for his funeral.
A man of letters, a true liberal and deeply cultured, Harry was also unfailingly courteous,
considerate and loyal. With a zest for life, an irresistible sense of humour and the ability to
reach out to people of all ages and from all walks of life, he was a much loved figure, his
company sought out to the end even by the young.
A Greek graduate student, Katerina Krikos, likewise found his personality irresistible when
they first met, in May 1975. They married a year later and remained deeply devoted to each
other till the end.
Harry died on 11 March 2014.
Richard Charles (1972)
Rick on the left, having flown the Spitfire
Steve Charles (1977) writes:
Rick Charles was one of the most high-ranking members of the RAF that The Perse has
produced. He joined the RAF Legal Branch as a Flight Lieutenant after taking a Law degree at
Nottingham University. After tours in Germany, Hong Kong and the First Gulf War he rose to
the rank of Air Vice-Marshal and Head of the Legal Branch. He was honoured by the Queen
as a Companion of the Order of the Bath in 2005.
He was always fascinated by aircraft and aviation history and had been a keen member of
the RAF section in the CCF at School. He obtained his private pilot’s license while at
University. More recently he flew in the skies around his home outside Cheltenham.
Boyhood dreams were realised when he flew in the gun turret of a Lancaster bomber, and
subsequently flew a Spitfire in the summer of 2012.
At School he had been a member of the 1st XV and 1st XI in hockey. He had a life-long passion
for rugby and became a season ticket holder of Gloucester, contributing to the game as a
Discipline Officer of the RFU, working on Disciplinary panels for Rugby Premiership matches
and the Churchill Cup. He had many other interests: long distance walks (he was a longserving Cotswold Way Volunteer); bird watching; beekeeping; Trustee of the RAF Charitable
Trust and The Royal International Air Tattoo.
He was happily married to Anne from 1979 and they had two sons, Philip and Thomas. Rick
retired from the RAF in 2009 and was hugely enjoying his wide portfolio of interests. He
derived particular joy from flying and walking the countryside. Unfortunately over Christmas
2012 he was diagnosed with a particularly aggressive brain tumour, and despite treatment
he died on 21 July 2013, aged 59.
After his death, his family and friends, including many OPs, wished to commemorate him,
and permission was granted to erect a bench on the section of the Cotswold Way that he
had cared for, just inside the Prestbury Butterfly Reserve above Cheltenham. The beautiful
oak bench, a fitting memorial to a thoroughly decent man, will provide rest to walkers that
pass by for many years to come. It has been expertly engraved with a Duke of Burgundy
butterfly (to signify the bench’s location) and a buzzard (for Rick’s love of flight and nature),
and also a tiny hidden bee. Rick is greatly missed by his family and many friends.
Colin Stuart (1947)
Mrs Vanessa Stuart writes:
Colin joined the Royal Regiment of Artillery and served in Malaya and Singapore. He learned
Mandarin Chinese with the Army and moved to the Foreign Office where he had postings in
Hong Kong, Malaysia and Singapore.
Music was always a very important part of his life and he continued to be involved in one
way or another through all overseas postings, indeed all his life. He was a talented and
versatile musician, from Musical Director for countless amateur dramatic productions, to
playing in philharmonic orchestras, to his greatest passion – jazz.
He played with Harry Gold and his Pieces of Eight and was a guest soloist with the BBC Big
Band. He played in Don Rendell’s Goldsmiths Big Band in the ‘70s where he met Len Phillips.
Len formed his own band in 1985 and Colin was the band’s last remaining founder member.
Once retired, he was able to enter a third career as a professional musician. His first full-time
gig was lead trumpet on the QE2 world cruise and he became a well-known face on the
London jazz circuit. He continued to play in the Len Phillips Big Band when it was taken over
by Joe Pettitt about four years ago.