Barry Quin

as Samuel Keifer

as Dr. Keith Simms

as Dr. Bennett

as Professor Sorvad

as Desmond Swarts

as Lionel Huxley (1 episode)

as Gervaise de Lutrelle (26 episodes)

as Solicitor (1 episode)

as Julian Roberts

as Mr. Scanlon (1 episode)

as The Hon. W. H. Lyttelton (4 episodes)

as Leutnant Hicks (4 episodes)

as Dr. Philip Grigg (1 episode)

as Richard Barwell (8 episodes)

as Hugo Brayford (4 episodes)

as Dr. Greg Miller (165 episodes)

as Engineer

as Francis Considine

as Francis Considine (1 episode)

as Ed Jarvis (1 episode)

as Greg (1 episode)

as Hugh Garthorne (1 episode)