[1] Born and raised in Belfast, where his father Daniel was a machinist and his mother a cleaner, Mornin left school at 15, taking a variety of jobs before joining the Royal Navy.
The Murderers (1985), set in East Belfast at the beginning of the 1970s, directed by Peter Gill at the National Theatre[3] was called by Irving Wardle "the work of an able and impassioned writer" and for which he won the George Devine award for most promising playwright.
This was followed in 1987 by Built on Sand at the Royal Court directed by Lindsay Posner and by Weights and Measures,[4] a black comedy based on the Dennis Nilsen murders, was enthusiastically received by an invited audience at the National Theatre studios in 1987 but considered too dark for a full-scale production.
His second play for the National, At Our Table (1991),[7] was a compelling study of the banality of evil, inspired by Primo Levi and with haunting music by Mornin's close friend Stephen Warbeck.
All Our Fault was later adapted for the film Nothing Personal[8][9] directed by Thaddeus O'Sullivan and for which Mornin was screenwriter and starred Ian Hart, John Lynch and Michael Gambon.