At a very early age, William, or Billy as he was known, moved with the family to live in Glengormley. Boyd was raised Presbyterian and attended the local primary school and Ballyclare High School.
At the age of 14, Boyd quit school to work and earn money to help support his family. He eventually joined the Ulster Group Theatre, where he learned the behind-the-scenes tasks of the theatre.
He became well known in Belfast for his contributions as a gravel-voiced policeman on the Ulster Radio programme "The McCooeys", the story of a Belfast family written by Joseph Tomelty. Boyd eventually worked his way up to character parts and then starring roles.
By nineteen he had toured Canada with summer stock companies. Boyd later recalled this as "the best performance I ever gave in my life". By the time he was 20, Boyd had a wide range of theatre experience, but he longed for the big stage. The Leicester Square Cinema across the street recruited him to usher attendees during the British Academy Awards in the early s.
During the awards ceremony, he was noticed by actor Sir Michael Redgrave , who used his connections to introduce Boyd to the director of the Windsor Repertory Group.
