Hardwicke made his first appearance on stage at the Lyceum Theatre, London, in 1912 during the run of Frederick Melville's melodrama The Monk and the Woman, when he took over the part of Brother John. During that year he was at Her Majesty's Theatre understudying, and subsequently appeared at the Garrick Theatre in Charles Klein's play Find the Woman, and Trust the People. In 1913 he joined Benson's Company and toured in the provinces, South Africa and Rhodesia. During 1914 he toured with Miss Darragh (Letitia Marion Dallas, d. 1917) in Laurence Irving's play The Unwritten Law, and he appeared at the Old Vic in 1914 as Malcolm in Macbeth, Tranio in The Taming of the Shrew, and the gravedigger in Hamlet, among other roles.