| Name | Character | Episodes |
|---|---|---|
| Brian Cox | Daddy | 6 |
| Paul Ritter | Bobby Waterhouse | 6 |
| Victoria Hamilton | Sarah Montag | 6 |
| Shaun Dooley | DC Jim Fenchurch | 6 |
| Tom Hughes | Joe Lambe | 6 |
| Jonathan Aris | Alan Montag | 6 |
| Chloe Pirrie | Wendy Straw | 6 |
| Zana Marjanović | Yulia | 6 |
| Judy Parfitt | Hester Waterhouse | 5 |
| Yevgeni Sitokhin | Odin | 5 |
| Marcel Iureș | Arkady | 4 |
| Gemma Chan | Chen Mei | 2 |
| Jay Simpson | Colin Blakefield | 2 |
| Velibor Topic | KGB Hood | 2 |
| Tim Bentinck | Home Secretary | 2 |
| Chris Cowlin | Member of Special Branch (uncredited) | 2 |
| Scott Handy | David Hexton | 1 |
| Anton Lesser | C | 1 |
| Rachael Stirling | Kate | 1 |
| Rachael Stirling | Kate Wilkinson | 1 |
| Emma Fielding | Valerie Parkwood | 1 |
| Andrew Bicknell | Martin | 1 |
| Adam James | George | 1 |
| Alistair Petrie | Andrew | 1 |
| Craig Conway | Philip Denmoor | 1 |
| Jon Glover | Public Information Film Narrator | 1 |
| Richard McCabe | Prime Minister | 1 |
| Ian Hanmore | Dennis Lamb | 1 |
| Georgina Rich | Alice | 1 |
| Goran Navojec | Bogdan Rodchenko | 1 |
| Joe Egan | The Big Fella | 1 |
| Todd Boyce | Hank Chambers | 1 |
| Doreene Blackstock | Nurse | 1 |
| Hermione Gulliford | Secretary to the Home Secretary | 1 |
| David Verrey | Edgar | 1 |
| Enzo Squillino Jr. | Hotel Proprietor | 1 |
| Julia Krynke | Embassy Woman | 1 |
| Laurentiu Possa | Hood | 1 |
| Yuri Klimov | Kasimir | 1 |
| Laurence Kinlan | IRA Man | 1 |
| Gabrielle Scharnitzky | Kitty | 1 |