Reggie (1 episode)

Self

Mr. Brownlow

Henry Angkatell (1 episode)

Sam's Grandfather

Mr. Wood

Wickfield

Heaviside

Ludovico H. Holly

Richard Bannerman

Zachariah

Tommy Bayne (1 episode)

Dr. Joseph

Earl of Arundel

Jonathan

Sir Arthur Conan Doyle

Patrick Siddons (1 episode)

Lord Stanley

Gov. John Bellingham

Dr. Watson (6 episodes)

Warnie Lewis

Dr. John Watson

Dr. John Watson

Kinloch (1 episode)

Dr. John Watson

Approved School Principal

Himself (1 episode)

Dr. John Watson

Dr. John Watson

Dr. Watson (11 episodes)

Dr. John H. Watson (28 episodes)

Gavin Barlow (1 episode)

Marcus

Dr. Pierre Dubois

Guy Phillips (1 episode)

Barry

Professor Proctor

Peter Carmody

Dr. Alan Lyle

Paediatrician

(1 episode)

Peter Topglass (4 episodes)

Brinson

Lord Dunning

Dieter Stahl

Enrico Fermi (7 episodes)

Christmas Humphries (1 episode)

Mr. Girton

Mr. Girton (1 episode)

Bellcourt (1 episode)

Donald Sanders (13 episodes)

Inspector Black

Biberstein (1 episode)

(1 episode)

Captain Paul Winter

(2 episodes)

Lieut. Colonel Rusper

Clive

Gareth (1 episode)

Paediatrician (1 episode)

Brinson (1 episode)

Gareth

Gifford (1 episode)

Gifford

Mike McCarthy

(1 episode)

(1 episode)

Dr. Paul Richards (3 episodes)

Charles Harold Calthrop

Arthur (13 episodes)

Capt. Pat Grant (28 episodes)

Stephen

Mitchell

Judas Iscariot

Lambert

Judas (2 episodes)

Pierre Chandebisse, Victor's Nephew

(6 episodes)

Dr. Frank Yarrow

Morris Dixon

Montano

Ulvik

George - English Boy (uncredited)