Alastair Sim as Millicent Fritton / Clarence Fritton

Joyce Grenfell as P.W. Sgt. Ruby Gates

George Cole as Flash Harry

Hermione Baddeley as Miss Drownder

Betty Ann Davies as Miss Waters

Renée Houston as Miss Brimmer

Beryl Reid as Miss Wilson

Irene Handl as Miss Gale

Mary Merrall as Miss Buckland

Joan Sims as Miss Dawn

Balbina as Mlle de St. Emilion

Jane Henderson as Miss Holland

Diana Day as Jackie

Jill Braidwood as Florrie

Annabelle Covey as Maudie

Pauline Drewett as Celia

Jean Langston as Rosie

Lloyd Lamble as Superintendent Kemp Bird

Richard Wattis as Manton Bassett

Guy Middleton as Eric Rowbottom-Smith

Arthur Howard as Wilfred Woodley

Michael Ripper as Albert Faning

Eric Pohlmann as The Sultan of Makyad

Sid James as Benny

Martin Walker as Hankinson

Noel Hood as Bilston School Mistress

Vivienne Martin as Arabella

Elizabeth Griffiths as Gladys

Andrée Melly as Lucretia

Belinda Lee as Amanda

Michael Kelly as Bill

Tommy Duggan as Joe

Paul Connell as Sam

Lorna Henderson as Fatima

Vivien Wood as Miss Anderson

Cara Stevens as Sultan's Secretary

Jerry Verno as Alf - the Bookmaker

Jack Doyle as Assistant Trainer

Arthur Mullard as Henchman (uncredited)

Carol White as Schoolgirl (uncredited)

Barbara Windsor as Schoolgirl (uncredited)