| Name | Character | Episodes |
|---|---|---|
| Michael Atkinson | Robert Shoesmith | 14 |
| Andrew Faulds | Ian Souter | 14 |
| Ann Morrish | Heather Keys | 14 |
| Roger Delgado | Boris Slankin | 1 |
| Peter Bowles | Dr. Fothergill | 1 |
| John Bluthal | Vladimir Kropotny | 1 |
| Derek Fowlds | Hughie | 1 |
| David Graham | Henry Thorne | 1 |
| Gerald Sim | Tony Kimber | 1 |
| Brian Wilde | Happy Dyer | 1 |
| Faith Brook | Dr. Bradbury | 1 |
| Gerald Harper | Hon. Arthur Keir | 1 |
| John Abineri | Mr. Milton | 1 |