| Claire Foy | Queen Elizabeth II |
| Matt Smith | Philip, Duke of Edinburgh |
| Victoria Hamilton | Queen Elizabeth the Queen Mother |
| Jeremy Northam | Anthony Eden |
| John Lithgow | Winston Churchill |
| Harriet Walter | Clemmie Churchill |
| Nicholas Rowe | Jock Colville |
| Pip Torrens | Tommy Lascelles |
| Harry Hadden-Paton | Martin Charteris |
| Clive Francis | Lord Salisbury |
| Billy Jenkins | Prince Charles |
| Verity Russell | Young Princess Elizabeth |
| Beau Gadsdon | Young Princess Margaret |
| James Hillier | Equerry (Buckingham Palace) |
| Will Keen | Michael Adeane |
| Jonathan Newth | Page (Buckingham Palace) |
| Jo Herbert | Mary Charteris |
| Thomas Padden | Page (Clarence House) |
| Ian Porter | U.S. Department Aide |
| Garrick Hagon | John F. Dulles |
| Alan Williams | Professor Hogg |
| Andrew Bone | F.O. Aide |
| Héléna Soubeyrand | Marie-Antoinette de Bellaigue |
| Sara Vickers | Marion Crawford |
| Michael Cochrane | Vice Provost Sir Henry Marten |
| Amy Doyle | Colville's Secretary |
| Paul Sheridan | Eden's Aide |
| Todd Boyce | U.S.A.F. General |
| Teddy Lewis | Groundskeeper |
| Andy Sanderson | Prince Henry Duke of Gloucester |
| Vash Singh | Crowd |
| Robert Strange | F.O. Telephonist |
| Lindy Barrett | Child on Riverbank |
| Stefan Kopiecki | Reporter |
| James M.L. Muller | Boyscout |
| Hugh O'Brien | Government Telephonist |
| Nick Owenford | State Delegate |
| Bo Ponomari | Martin (footman) |