Gary Oldman character Winston Churchill
Kristin Scott Thomas character Clementine Churchill
Lily James character Elizabeth Layton
Stephen Dillane character Edward Wood, 3rd Viscount Halifax
Ronald Pickup character Neville Chamberlain
Ben Mendelsohn character George VI
Nicholas Jones character John Simon, 1st Viscount Simon
Samuel West character Anthony Eden
David Schofield character Clement Atlee
Richard Lumsden character Major-General Hastings Ismay
Malcolm Storry character General Sir Edmund Ironside
Hilton McRae character Arthur Greenwood
Benjamin Whitrow character Sir Samuel Hoare
Joe Armstrong character John Evans
Adrian Rawlins character Air Chief Marshal Sir Hugh Dowding
David Bamber character Vice-Admiral Bertram Ramsay
David Strathairn character Franklin D. Roosevelt (voice)
Jeremy Child character James Stanhope, 7th Earl Stanhope
Brian Pettifer character Sir Kingsley Wood
Michael Gould character Charles Vane-Tempest-Stewart, 7th Marquess of Londonderry
John Atterbury character Sir Alexander Cadogan
Charley Palmer Rothwell character Miles Aldridge
Hannah Steele character Abigail Walker
Philip Martin Brown character Sawyers
Nia Gwynne character Alice Simpson
Faye Marsay character Sybil
Jordan Waller character Randolph Churchill
Mary Antony character Mary Churchill
Bethany Muir character Sarah Churchill
Anna Burnett character Pamela Churchill
James Eeles character Maurice Baker
Roisin O'Neill character Agnes Dillon
Joanna Neary character Jerome Margaret
Flora Nicholson character Jessie Sutton
Richard Glover character Brigadier Nicholson
Paul Leonard character Admiral Dudley Pound
Eric MacLennan character Tom Leonard
Tom Ashley character Ramsay Staffer
Pip Torrens character BBC Producer
Bronte Carmichael character Young Girl on Train
Patsy Ferran character Maid
John Locke character Oliver Wilson
James Harkness character AD Nicholl (Secretary #1)
Joshua James character W D Wilkinson (Secretary #2)
Kieran Buckeridge character Cecil Beaton
Adolf Hitler character Self (archive footage) (uncredited)