Her film début was an uncredited part in The Man Behind the Mask (1936); she was first credited as Polly Shepherd in The Last Adventurers (1937), and she appeared in 64 films over the next 26 years. She had small parts in three early Powell and Pressburger films: The Spy in Black (1939), Contraband (1940) and A Canterbury Tale (1944), Holiday Camp (1947) and, towards the end of her career, appeared in Inn for Trouble (1960), Doctor in Love (1960), Raising the Wind (1961), What a Carve Up! (1961), Over the Odds (1961), We Joined the Navy (1962), On the Beat (1962), Nurse on Wheels (1963) and Hide and Seek (1964). In Holiday Camp she gave a fine dramatic performance of a pathetic and sad spinster who is lured to her death and is the murder victim, quite different from her usual comedy roles. She is perhaps best remembered for her role as Edie Hornett opposite Peggy Mount in the comedy Sailor Beware! (1956). She played “Brother” Lil in the British television comedy series The Rag Trade (1961–1963), and also appeared in four Carry On films: Carry On Constable (1960), Carry On Regardless (1961), Carry On Cruising (1962) and Carry On Cabby (1963). Cannon, whose first name sometimes appears incorrectly as “Esme”, retired in 1963 after Carry On Cabby. Cannon died in 1972. She was 66. She was buried at St Benoit-la-Forêt in France  Her elusiveness was such that her former colleagues and friends discovered she’d died only after a “Where are they Now?” feature in films and filming a number of years after her death. She was played by the actress Marcia Warren in the 2011 TV play Hattie, a drama based on the career of Hattie Jacques. The play featured a number of scenes with the two actresses on the set of Carry On Cabby.