"Tis the luck of the Irish," Boyd lamented when shooting resumed on "Cleopatra" with the Welchman Burton in the choice Marc Antony role.
Boyd, who stood 6 feet 1 inch and weighed 185 pounds, was noted for his ability to switch easily into any mood for which a script called.
"Indeed", Times critic Charles Champlin wrote in 1966, "the variety of parts Boyd has played over the years has been such as to forestall the emergence of a clearcut and indelible Boyd trademark, that magnetizing personality which attracts the manic clamor of fandom, which is in turn the mark of the star.
"It is probably an ironic tribute to Boyd's craft that he should, in effect, be remembered for his roles rather more than for himself."
Boyd was born William Miller near Belfast on the Fourth of July - a prophetic day, he said in 1963 when he took the oath as a U.S. citizen. He was the youngest of nine children.
He made his debut as a radio actor at 8, and, when 18, he joined the Ulster Group Theater.
Boyd later went to England to further his acting career. He toured with smal theatrical groups and, between engagements, held various jobs, including that of a cafeteria worker and a doorman at a movie house.
It was while holding down the doorman job that he met Sir Mickael Redgrave, who arranged for Boyd to try out with the Windsor Repertory Company. Within two weeks, Boyd landed the lead in one of the company's plays.
He appeared as a leading man in more than a dozen productions, including "A Streetcar Named Desire".
In the late 1950's he made several movies in Britain. One of them, "The Man Who Never Was", in which he played an Irish fanatic, won him critical acclaim and offers from Hollywood.
Boyd appeared often in television roles in recent years, including the lead in the Hallmark Hall of Fame production of "The Hands of Cormac Joyce", based on a story by Leonard Wibberley, in 1972.
Boyd and his second wife made their home in Tarzana. They had no children. He was formerly married to Mariella di Sarzana. That marriage ended in divorce in 1959.