Gary Oldman Winston Churchill Kristin Scott Thomas Clementine Churchill Lily James Elizabeth Layton Stephen Dillane Edward Wood, 3rd Viscount Halifax Ronald Pickup Neville Chamberlain Ben Mendelsohn George VI Nicholas Jones John Simon, 1st Viscount Simon Samuel West Anthony Eden David Schofield Clement Atlee Richard Lumsden Major-General Hastings Ismay Hilton McRae Arthur Greenwood Benjamin Whitrow Sir Samuel Hoare Adrian Rawlins Air Chief Marshal Sir Hugh Dowding David Bamber Vice-Admiral Bertram Ramsay David Strathairn Franklin D. Roosevelt (voice) Brian Pettifer Sir Kingsley Wood Michael Gould Charles Vane-Tempest-Stewart, 7th Marquess of Londonderry Charley Palmer Rothwell Miles Aldridge Hannah Steele Abigail Walker Philip Martin Brown Sawyers Nia Gwynne Alice Simpson Pip Torrens BBC Producer