How Did John Shirley-Quirk Die?

John Stanton Shirley-Quirk CBE was an English bass-baritone. A member of the English Opera Group from 1964 to 1976, he gave premiere performances of several operatic and vocal works by Benjamin Britten, recording these and other works under the composer's direction. He also sang and recorded a wide range of works by other composers, ranging from Handel through Tchaikovsky to Henze.