Agatha Christie used her grandmother as a model for Miss Marple, new tapes reveal Lying undisturbed for more than 40 years, audio tapes bearing the unmistakeable voice of Agatha Christie have been discovered that show how she modelled Miss Marple on her own grandmother. By Stephen Adams, Arts Correspondent Her grandson Mathew Prichard stumbled upon 27 of the half-hour long tapes in a dusty cardboard box as he cleaned out a storeroom in Greenway, the Georgian property overlooking the Dart estuary in Devon that Christie called "the loveliest place in the world". The tapes, which nobody knew existed, are the raw material on which part of her autobiography was based. Working alone at her own unhurried pace, the ageing Christie dictated the tapes on a Grundig Memorette machine in the mid 1960s. Her rich, authoritative voice offers a wealth of insights into her life and how she developed her most beloved characters. Among them is her description of Jane Marple - and how she partially based the genteel sleuth on her grandmother. Although she insisted that Miss Marple was in no way "a picture of my grandmother," she did admit the two shared an important trait. Speaking with a calm and deliberate authority, Christie said of her grandmother: "Although a completely cheerful person, she always expected the worst of anyone and everything. And with almost frightening accuracy (she was) usually proved right." Her grandmother would say "I shouldn't be surprised if so-and-so was going on," Christie recalled. "And although with no grounds for these assertions, that was exactly what was going on." Christie did not intend Miss Marple to be a permanent character, the tapes reveal. But the sharp-witted spinster "insinuated herself so quietly into my life that I think I hardly noticed her arrival." Rolling the 'r' to dramatic effect, she dictated: "I didn't know then that she would become a rival to Hercule Poirot." Another extract from the tapes, revealed today by the Christie Archives Trust to mark the 118th anniversary of her birth, explain that she thought the fastidious Hercule Poirot and the indomitable Miss Marple should never meet. Mr Prichard said it was "eerie" to hear her voice more than 30 years after her death. Describing his feelings on listening to it, he said: "Comforting isn't quite the word, but they are very evocative." He thought his grandmother's voice was able to communicate far more than the written word alone. Mr Prichard found the tapes months ago after deciding to clean out a storeroom in the house, which the family has handed to the National Trust. His mother Rosalind Hicks was not the type to catalogue her mother's possessions, he said, so when he found the unlabelled tapes he had no idea what was on them. He had assumed the tapes' contents were "irretrievable" as the ancient Grundig recorder was broken, its defunct batteries corroded. But earlier this summer he decided to call a friend with a knowledge of old tape machines. After raising an eyebrow, the friend managed to get it working again. Laura Thompson, author of the biography 'Agatha Christie: An English Mystery', said the "extraordinary" find was of great value because Christie rarely gave interviews. "She did speak on the radio to the BBC a couple of times in the 1950s but she did very, very little. It is a thrill to hear her voice."