Hugh Sinclair as Humphrey Mansfield

Griffith Jones as James Brodie

Francis L. Sullivan as Leon Poiccard

Frank Lawton as James Terry

Anna Lee as Ann Lodge

Alan Napier as Sir Hamar Ryman M.P.

Basil Sydney as Frank Snell

Lydia Sherwood as Myra Hastings

Edward Chapman as B.J. Burrell

Athole Stewart as Police Commissioner

George Merritt as Inspector Falmouth

Garry Marsh as Bill Grant

Ellaline Terriss as Lady Willoughby

Roland Pertwee as Mr Hastings

Eliot Makeham as Simmons

Frederick Piper as Pickpocket (uncredited)

Henrietta Watson as Mrs. Truscott

Jon Pertwee as Rally campaigner (uncredited)

Liam Gaffney as Taxi driver (uncredited)

Manning Whiley as (uncredited)

Neal Arden as (uncredited)

Basil Radford as (uncredited)

Edward Rigby as (uncredited)

Paul Sheridan as (uncredited)

Winston Churchill as Self (archive footage) (uncredited)

Arthur Hambling as Constable Benham

Bryan Herbert as Taxi driver (uncredited)

Adolf Hitler as Self (archive footage) (uncredited)

James Knight as Policeman Outside Parliament (uncredited)

Percy Parsons as American Broadcaster (uncredited)

Charles Paton as Platform Speaker (uncredited)

Percy Walsh as Prison Governor (uncredited)