Throughout his professional life as an Author (he always used the capital), Malcolm Saville wrote to anyone who contacted him, running an active and personalised fan club. He took this opportunity to encourage his fans to buy more books. Some were adults, and to these he tended to admit more, such as his exhaustion with the Lone Pine series.
Between 1978 and 1981, Malcolm Saville corresponded with Mary Cadogan, the writer on children's literature. She was planning a biographical book which did not in the end come to pass.
You can read some of these, and other letters on here