Sharp's career began in 1965, with the publication of his acclaimed first novel, A Green Tree in Gedde. It was the first part of a proposed trilogy, but Sharp completed only one more novel, The Wind Shifts (1967), before migrating to Hollywood and becoming a much sought after screenwriter.
Sharp's most productive period was the early and mid-1970s, when five of his screenplays became high-profile Hollywood productions, most of them dealing with quintessentially American themes and characters. At least three are now recognized as classics of the New American Cinema of the 1970s: Peter Fonda's The Hired Hand, Robert Aldrich's Ulzana's Raid and Arthur Penn's Night Moves.
Since the 1980s, Sharp has been mostly writing for American television. His only completed film projects have been Sam Peckinpah's swan song The Osterman Weekend (1982) and Rob Roy (1995). While Rob Roy led to Sharp's rediscovery as a serious and important writer, subsequent film assignments remained elusive.
Two current Sharp projects in production are Burns (previously "Clarinda"), a biography of Scotland's national poet Robert Burns, starring Gerard Butler and Julia Stiles, and Dean Spanley from the novel by Irish writer Lord Dunsany, due in cinemas in 2008.
Sharp is the father of actress Rudi Davies, by writer Beryl Bainbridge.