Born Sam Cowan in Lambeth, London, in 1881, Mayo made his first appearance at a Sunday morning concert at the Victoria Club in the Blackfriars Road. He first appeared in music hall in 1898 at the Alhambra, Sandgate. He often dressed in a dressing gown and motoring cap, and sang comic songs including ‘She Cost Me Seven and Sixpence’ and ‘I’ve Only Come Down for the Day’. He was often billed as ‘The Immobile One’ because of his trick of standing still on stage with a lugubrious expression while singing comic songs. Later he toured his own revues and was popular in pantomime.

Mayo went on to tour with his own revues, and appear in variety and pantomime a review of his act heading the variety bill at the Theatre Royal Aldershot in June 1931 the reviewer called him: 'The inimitable Sam Mayo, one of England's best- known comedians and humorists' [sic] adding: 'Part of Sam's charm is his pained expression while he sings the most funny songs, playing his own accompaniments on a grand piano.'