Born in Woolwich, south London, Ashley trained as a teacher at Trent Park College of Education after his National Service in the RAF. His teaching career included thirty years as headteacher. Ashley is also an author of books for children and young adults. His debut novel, The Trouble with Donovan Croft, published in 1974, won The Other Award, an alternative to the Carnegie Medal. A Kind of Wild Justice (1978), Running Scared (1986), and Little Soldier (1999) were commended runners up for the Carnegie Medal from the Library Association, recognising the year's best children's book.