Hay Petrie went to St Andrew’s Academy, Dundee, and St Andrew’s University, where he first discovered the stage. In 1915 he joined the Royal Scots (Lothian Regiment) as a Second Lieutenant. After the war he studied with Rosina Filippi joining the Old Vic Company appearing as "Starveling" in A Midsummer Night’s Dream in 1920. In 1924 Albert de Courville brought Hay Petrie into Vaudeville with The Looking Glass, in which he sang "Oh Shakespeare you’re the best of all but you can’t fill the fourteen shilling stall". His first film part was Many Waters in 1931. Hay Petrie struggled with alcoholism, but was much loved by audiences and players. He was never more at home than when he was playing parts from the classical theatre, and for many he was the Shakespearian Clown of the early 1920s.