 Byam Shaw was born in London, the youngest of five siblings (four sons and one daughter) born to artist John Byam Liston Shaw and his wife, Caroline Evelyn Eunice Pyke-Nott (1870–1959), also an artist.He was educated at Westminster School, where his contemporaries included his elder brother, James Byam Shaw, later a well-known art historian, and John Gielgud, who became a lifelong friend and professional colleague.The actor Michael Denison, biographer of Byam Shaw in the "Oxford Dictionary of National Biography" writes that Byam Shaw made his professional stage debut in August 1923 with no prior training.