Mortimer died at his home near Henley, Buckinghamshire, in the company of his second wife, Penny, and daughters Emily and Rosie.
Mr. Mortimer was a barrister whose work helped end the Lord Chamberlain's censorship of stage productions with the 1968 Theatres Act. His beloved barrister character, Rumpole, first emerged in 1975 as a BBC "Play For Today," and was expanded in a series of novels and a hit ITV television series starring Leo McKern.
Mr. Mortimer's autobiographical 1963 play A Voyage Round My Father was staged in 2006 by the Donmar Warehouse. First written as a radio play, it charted his relationship with his blind barrister father.
Mr. Mortimer was the adaptor-screenwriter of the internationally famous 1981 TV series "Brideshead Revisited," from the novel by Evelyn Waugh. He also penned the film "Tea With Mussolini."
His Legal Fictions, a double bill comprising his first play The Dock Brief and Edwin, played at the Savoy Theatre on the West End in early 2008. His one Broadway credit was a 1992 translation of the Georges Feydeau farce A Little Hotel on the Side, for the National Actors Theatre.
Mr. Mortimer spent a decade as chairman of the board of the Royal Court, and another decade as its president. He received a knighthood in 1998.