- Louise Pajo - Miss Scott
- Peter Blythe - 2nd Officer
- Conrad Phillips - Skipper
- Geoffrey Hinsliff - Hotel Clerk
- John Stratton - John Croxley
- Michael Kilgarriff - Steiner
- Allan Cuthbertson - Jack Newton
- John Levene - Interceptor Pilot
- David Healy - Joe Franklin
- Suzan Farmer - Tina Duval
- Eleanor Summerfield - Muriel Thompson
- Richard Vernon - Pa Stone
- Robin Bailey - Kofax
- Tracy Reed - Jane Carson
- Patrick Allen - Turner
- Jane Merrow - Jo Fraser
- Jack Hedley - Webb
- Mike Pratt - Clem Mason
- Tessa Wyatt - Catherine Frazer
- David Daker - SHADO Guard
- Basil Dignam - Cabinet Minister
- Nigel Lambert - Moonbase Operative
- David Warbeck - Skydiver Captain
- Douglas Wilmer - Dr. Ward / Dr. Brünner
- Russell Napier - Dr. Green
- Philip Latham - Blake
- Paul Maxwell - Lt. Jim Lewis
- Charles Tingwell - Captain Beaver James
- Tutte Lemkow - Singleton
- George Cole - Paul Roper
- Jeffrey Segal - Monsieur Duval
- Patrick Jordan - Russian Base Cmdr.
- Jean Marsh - Janna
- James Cosmo - Lt. Anderson
- Annette Kerr - Nurse
- Edwin Richfield - Admiral Sheringham
- Deborah Grant - Linda Simmonds
- Gary Raymond - Colonel John Grey
- Clinton Greyn - Mark Tanner
- Windsor Davies - Morgan
- Adrienne Corri - Liz Newton
- Al Mancini - Lt. Andy Conroy
- Neil McCallum - Carl Mason
- Donald Tandy - Gateman
- Alan Tilvern - U.S. Delegate
- Patrick Mower - Cass Fowler
- Oscar James - Plain Clothes Officer
- Richard Aylen - Alien
- Susan Jameson - Anne Stone
- Pippa Steel - Diane
- Colin Gordon - Albert Thompson
- Godfrey James - Game Warden
- Tom Adams - Captain Lauritzen
- David Savile - Hospital Doctor
- Jack May - English Delegate
- Michael Jayston - Russell Stone
- Christopher Timothy - Skydiver 3 Navigator
- Lois Maxwell - Miss Holland
- Stuart Damon - Howard Byrne
- Jean Wladon - Actor
- Shane Rimmer - Lt. Bill Johnson
- Shane Rimmer - CIA Agent
- Wanda Ventham - Colonel Virginia Lake
- Anthony Chinn - Alien
- Anthony Chinn - Lt. Tony Chin
- Gary Files - Phil Wade
- Matthew Roberton - Dr. Harris
- Matt Zimmerman - Co-Pilot
- Paula Li Shiu - Tsi
- Arthur Cox - Louis
- Robert Swann - William Grant
- Ray Armstrong - Rescuer
- Michael Mundell - Ken Matthews
- Hugh Armstrong - SHADO Mobile 3 Officer
- Dennis Plenty - SHADO Mobile 1 Personnel
- David Weston - Mitchell
- David Weston - Rescuer
- Keith Grenville - Dawson
- Sonia Fox - Carol Roper
- Peter Gordeno - Capt. Peter Carlin
- Peter Gordeno - Capt. Carlin
- Burnell Tucker - G.S.P. 4 Co-Pilot Scott
- Burnell Tucker - Albatross Pilot Turner
- Drewe Henley - Maddox
- Tom Oliver - Doctor
- Tom Oliver - Technician
- Frank E. Stranges - Doctor Stranges
- Peter Burton - Dr. Murray
- Peter Burton - Perry
- John Breslin - Reed
- Georgina Moon - Skydiver Operative
- Georgina Moon - Skydiver Operative Lt. Sylvia Howell
- Barnaby Shaw - John Rutland
- John Lyons - Studio Guard
- John Lyons - SHADO Guard
- Philip Madoc - Steven Rutland
- Philip Madoc - Ship's Capt.
- Peter Halliday - Dr. Segal
- Quinn O'Hara - Sylvia Graham
- Alan Tucker - Lunar Module Pilot
- Alan Tucker - Navigator
- Alan Tucker - Tracking Station Operative
- Steven Berkoff - Captain Steve Minto
- Steven Berkoff - Capt. Steve Minto
- Mary Merrall - Mrs. O'Connor
- Ralph Ball - Film Director
- Andrea Allan - Nurse
- Andrea Allan - Moonbase Operative Carol Miller
- Janos Kurucz - Russian Astronaut
- Keith Alexander - SHADO Radio Operator
- Keith Alexander - Lt. Ford
- Paul Tamarin - Russian Astronaut
- Penny Spencer - SHADO Operative
- Suzanne Neve - Mary Straker
- Suzanne Neve - Mary Rutland
- Noel Davis - Artist's Agent
- Paul Greenhalgh - Assistant Director
- Mark Hawkins - Astronaut
- Mark Hawkins - Interceptor Pilot
- Anouska Hempel - Skydiver Operative
- Anouska Hempel - SHADO Radio Operator Tamara Paulson
- James Beckett - Dr. Young
- Frank Mann - Rocket Launch Controller
- Jeremy Wilkin - Skydiver Navigator
- Jeremy Wilkin - Skydiver Navigator Lt. Gordon Maxwell
- Michael Forrest - Security Officer
- Frank Tregear - Porter
- Donald Pelmear - Estate Agent
- Michael Nightingale - Mary's Father
- Maxwell Shaw - Dr. Shroeder
- David Sumner - Captain Frank Craig
- Antonia Ellis - Joan Harrington
- John Golightly - Holden
- Alan Haywood - SHADO Diver Ross
- Grant Taylor - Gen. James Henderson
- Grant Taylor - Gen. Henderson
- Grant Taylor - General Henderson
- Gito Santana - Alien
- Alexis Kanner - Lt. Jim Regan
- Geraldine Moffat - Jean Regan
- Jimmy Winston - Rating
- Gordon Sterne - German Delegate
- Gordon Sterne - Helmsman Ellis
- Stephanie Beacham - Sarah Bosanquet
- Derren Nesbitt - Colonel Craig Collins
- Nigel Gregory - Ben Culley
- Nigel Gregory - Security
- Michael Stevens - Chauffeur
- Roland Culver - Sir Esmond
- Robert Grange - Moonbase Doctor
- Nancy Nevinson - Housekeeper
- Rona Newton-John - Nurse
- David Collings - Daniel Clark
- Craig Hunter - G.S.P. 4 Pilot Hudson
- Craig Hunter - Lt. Dale
- Gavin Campbell - Police Motorcyclist
- Alexander Davion - The Executive
- Peter Davies - Fairfield Tracker Station Guard
- Robin Hawdon - Skydiver 3 Captain
- Hans De Vries - Security
- Mark York - Skydiver 3 Engineer
- Aidan Murphy - Room 22 Guard
- Fredric Abbott - Seaman
- Richard Caldicot - Film Producer
- David Griffith - Underwater Cameraman
- Keith Bell - Film Director
- Gerald Cross - Insurance Man
- Barry Stokes - Skydiver Engineer
- Ron Pember - Casting Agent
- Kirsten Lindholm - Actress
- John J. Carney - Studio Security Man
- Larry Taylor - Mexican Bandit
- Ricardo Montez - Mexican Bandit
- Bill Morgan - Mexican Bandit
- Gabrielle Drake - Lt. Ellis
- James Marcus - SHADO Operative
- Stanley McGeagh - SHADO Guard
- Stephan Chase - Film Director
- Paul Greaves - 2nd Assistant Director
- Christian Roberts - Tim Redman
- John Garrie - Van Driver
- Christopher Robbie - Bomb Disposal Expert
- Basil Moss - Dr. Frazer
- Basil Moss - Doctor
- Cyril Frankel
- Alan Perry
- Ken Turner
- Ron Appleton
- Jeremy Summers
- David Lane
- Dennis Spooner
- Alan Fennell
- Alan Pattillo
- Sylvia Anderson
- Bob Bell
- Ian Scott Stewart
Steven Berkoff interpreta a Capitano Steve Minto en la serie.
James Cosmo interpreta a Lt. Anderson en la serie.
Adrienne Corri hace el papel de Liz Newton.
Paul Maxwell interpreta a Lt. Jim Lewis en la serie.
Ed Bishop interpreta a Cmdr. Ed Straker en la serie.
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