Roger Moore as Harold Pelham

Anton Rodgers as Tony Alexander

Olga Georges-Picot as Julia Anderson

Freddie Jones as Dr. Harris

Hugh Mackenzie as James Pelham

Kevork Malikyan as Luigi

Thorley Walters as Frank Bellamy

Ruth Trouncer as Miss Bird

Hildegard Neil as Eve Pelham

John Welsh as Sir Charles Freeman

Edward Chapman as Barton

Laurence Hardy as Mason

Charles Lloyd Pack as Jameson

Gerald Sim as Morrison

Aubrey Richards as Research Scientist

Anthony Nicholls as Sir Arthur Richardson

John Carson as Ashton

John Dawson as Barber

Alastair Mackenzie as Michael

James Payne as Taxi Driver (uncredited)