Gary Oldman
Winston Churchill
David Schofield
Clement Atlee
Adrian Rawlins
Air Chief Marshal Dowding
Kristin Scott Thomas
Clemmie
Stephen Dillane
Viscount Halifax
David Strathairn
President Roosevelt (voice)
Demetri Goritsas
Cabinet Secretary Bridges
Nicholas Jones
Sir John Simon
David Bamber
Admiral Ramsay
Philip Martin Brown
Sawyers
Eric MacLennan
Tom Leonard
Ronald Pickup
Neville Chamberlain
Pip Torrens
BBC Producer
Samuel West
Sir Anthony Eden
Hilton McRae
Arthur Greenwood
Ben Mendelsohn
King George VI
Benjamin Whitrow
Sir Samuel Hoare
Brian Pettifer
Lord Kingsley Wood
Malcolm Storry
General Ironside
Richard Lumsden
General Ismay
Jeremy Child
Lord Stanhope
Richard Glover
Brigadier Nicholson
Sarah Flind
Cook
Joe Armstrong
John Evans
John Atterbury
Sir Alexander Cadogan
Robin Pearce
Ernle Hastings
Lily James
Elizabeth Layton
Paul Ridley
House of Commons Speaker
Michael Bott
Equerry
Mario Hacquard
Daladier
Faye Marsay
Sybil
Flora Nicholson
Jessie Sutton
Paul Leonard
Admiral Dudley Pound
Joshua James
W D Wilkinson (Secretary #2)
Olivier Broche
Reynaud
Charley Palmer Rothwell
Christopher Wilson (Photographer)
Michael Gould
Lord Londonderry
Anna Burnett
Pamela Churchill
Bethany Muir
Sarah Churchill
Jordan Waller
Randolph Churchill
Hannah Steele
Abigail Walker
Patsy Ferran
Maid
Johnny Otto
Member of Parliament (uncredited)
Imogen King
Teenage Girl at Tube Map
Joshua Higgott
Reporter
Tom Ashley
Ramsay Staffer
James Harkness
AD Nicholl (Secretary #1)
Nia Gwynne
Alice Simpson
Bronte Carmichael
Young Girl on Tube
Mary Antony
Mary Churchill
James Eeles
Maurice Baker
Roisin O'Neill
Agnes Dillon
Kieran Buckeridge
Cecil Beaton
John Locke
Oliver Wilson