Kieron Moore as Cmdr. Michael Haydon

Lois Maxwell as Kim Hamilton

Donald Wolfit as Prof. Merrity

Bryan Forbes as Jimmy Wheeler

Jimmy Hanley as Larry Noble

Barry Keegan as Lefty

Walter Hudd as Professor Blandford

Donald Gray as Captain Ross

Thea Gregory as Barbara Noble

Shirley Lawrence as Ellen

Peter Neil as Tony

Ryck Rydon as Reporter

Ronan O'Casey as Reporter

Robert O'Neil as Reporter

Alan Gifford as Colonel Galloway

Charles Richardson as General Barnett

Carl Jaffe as Professor Bechstein

Leonard Sharp as Thomas the Watchman (uncredited)

Paul Beradi as Reporter (uncredited)

Patrick Halpin as Reporter (uncredited)

Terry Randall as Reporter (uncredited)

Bill Nagy as Reporter (uncredited)

Terry Randall as Reporter (uncredited)

John Wilder as Reporter (uncredited)

Johnny Wyne as Reporter (uncredited)

Trevor Reid as Simmons the Technician (uncredited)

Bernard Bresslaw as Technician (uncredited)

Alastair Hunter as Technician (uncredited)

Jane Dore as Young Girl (uncredited)

Frank Sieman as Gatekeeper (uncredited)

John Baker as Official (uncredited)

Tony Quinn as Jack the Barman

Tony Quinn as Jack the Barman (uncredited)