He was born Glencairn Alexander Byam Shaw in London, the son of artist John Liston Byam Shaw. After a youthful relationship with the poet, Siegfried Sassoon (who remained one of his closest friends), he married the actress, Angela Baddeley. As an actor, he worked mostly in the theatre and during the 1930s he began directing in the West End. Between 1947 to 1956 he was the director of the Old Vic Theatre School, part of the Old Vic Theatre Centre run by Michel Saint-Denis which also included the Young Vic run by George Devine. From 1957 to 1959 he was director of the Shakespeare Memorial Theatre in Stratford-upon-Avon.