Betty's debut was in Belfast, before he was 12, in an English version of Voltaire's Zaïre. He was successful in Dublin, Glasgow, and Edinburgh. In 1804, when he first appeared at Covent Garden, London, troops were called out to preserve order, so great was the crush to obtain admittance. Later he played the great tragic roles of Shakespeare at Covent Garden and Drury Lane, where he received an unprecedented salary. George III presented him to the Queen, and William Pitt on one occasion adjourned the House of Commons so that members could see Master Betty's performance as Hamlet. In 1808 he made his final appearance as a boy actor and entered Christ's College, Cambridge. His attempt in 1812 to perform again was ill received. He retired completely in 1824 and lived off his fortune.