Gary Oldman as Winston Churchill

Stephen Dillane as Viscount Halifax

Lily James as Elizabeth Layton

Ronald Pickup as Neville Chamberlain

Ben Mendelsohn as King George VI

Kristin Scott Thomas as Clemmie

Nicholas Jones as Sir John Simon

Samuel West as Sir Anthony Eden

David Schofield as Clement Atlee

Richard Lumsden as General Ismay

Malcolm Storry as General Ironside

Hilton McRae as Arthur Greenwood

Benjamin Whitrow as Sir Samuel Hoare

Joe Armstrong as John Evans

Adrian Rawlins as Air Chief Marshal Dowding

David Bamber as Admiral Ramsay

Paul Leonard as Admiral Dudley Pound

David Strathairn as President Roosevelt (voice)

Eric MacLennan as Tom Leonard

Philip Martin Brown as Sawyers

Demetri Goritsas as Cabinet Secretary Bridges

Jordan Waller as Randolph Churchill

Alex Clatworthy as Diana Churchill

Mary Antony as Mary Churchill

Bethany Muir as Sarah Churchill

Anna Burnett as Pamela Churchill

Jeremy Child as Lord Stanhope

Brian Pettifer as Lord Kingsley Wood

Michael Gould as Lord Londonderry

Paul Ridley as House of Commons Speaker

Robin Pearce as Ernle Hastings

Michael Bott as Equerry

Olivier Broche as Reynaud

Mario Hacquard as Daladier

Pip Torrens as BBC Producer

Edmund Wiseman as Actor

Hannah Steele as Abigail Walker

Nia Gwynne as Alice Simpson

Ade Dee Haastrup as Marcus Peters

James Eeles as Maurice Baker

Flora Nicholson as Jessie Sutton

Bronte Carmichael as Young Girl on Tube

Roisin O'Neill as Agnes Dillon

John Locke as Oliver Wilson

Joanna Neary as Margaret Jerome

Richard Glover as Brigadier Nicholson

Tom Ashley as Ramsay Staffer

Joshua Higgott as Reporter

Imogen King as Teenage Girl at Tube Map

Miles Gallant as Naval Map-Room Officer

Faye Marsay as Sybil

John Atterbury as Sir Alexander Cadogan

James Harkness as AD Nicholl (Secretary #1)

Joshua James as W D Wilkinson (Secretary #2)

Charley Palmer Rothwell as Christopher Wilson (Photographer)

Patsy Ferran as Maid

Sarah Flind as Cook

Steffan Donnelly as Back Bencher

Kieran Buckeridge as Cecil Beaton

Johnny Otto as Member of Parliament (uncredited)

Nick Howden-Steenstra as Sentry (uncredited)