Maria Palmer is a pseudonym of Terrance Dicks.
Terrance Dicks is an English writer and former script editor, best known for his work in television and as the author of many popular children's books during the 1970s and 1980s.
His best known association during his television career was with Doctor Who, working as a writer and - from 1968 to 1974 - the program's script editor. He also adapted many of the televised stories into novelisations for Target Books.
Source: Wikipedia