Sangster originally worked as a
production assistant at Hammer Films, as well as being an
assistant director,
second unit director and production manager. After Hammer's success with
The Quatermass Xperiment, he was approached to write
X the Unknown, to which he replied "I'm not a writer. I'm a production manager." According to him, Hammer Films' response was: "Well, you come up with a couple of ideas and if we like it, we'll pay you. If we don't like it, we won't pay you. You're being paid as a production manager, so you can't complain." Sangster later turned to direction with
The Horror of Frankenstein and
Lust for a Vampire (both 1970) for the studio, but with far less success. His third (and last) film as director was
Fear in the Night (1972), which resurrected the psychological woman-in-peril thriller he had begun with his script for
Taste of Fear (1961). All three of the films he directed featured actor
Ralph Bates, a friend of Sangster's and one of Hammer's better-known performers for the company during the 1970s. Sangster scripted and produced two films for
Bette Davis,
The Nanny (1965) and
The Anniversary (1968). His other scriptwriting credits included
The Siege of Sidney Street (1960), which starred
Donald Sinden and in which Sangster appeared as
Winston Churchill. His many television screenwriting credits include
Kolchak: The Night Stalker, ''
Movin' On, The Magician, B. J. and the Bear, Most Wanted, Ironside, McCloud, The Six Million Dollar Man and Wonder Woman''. He is also the author of the novels
Touchfeather;
Touchfeather, Too;
Foreign Exchange;
Private I (aka
The Spy Killer);
Snowball;
Hardball; and
Blackball; all of which have been republished by
Brash Books. His other books include the novel
Your Friendly Neighborhood Death Peddler, the non-fiction memoir
Do You Want it Good or Tuesday? and the 2003
screenwriting manual,
Screenwriting: Techniques for Success. In 2019, Brash Books announced the discovery of an unpublished Sangster novel,
Fireball, which they released in 2020. ==Personal life==