- Colin Gordon - Number Two
- Leo McKern - Former Number Two
- Derren Nesbitt - New Number Two
- Eric Portman - Number Two
- Ronald Radd - Rook
- David Bauer - The Judge / Number Two
- Paul Eddington - Cobb
- John Sharp - Number Two
- Mary Morris - Number Two
- Anton Rodgers - Number Two
- Donald Sinden - The Colonel
- Nigel Stock - The Colonel / Number Six / Seltzman
- Alexis Kanner - Number Forty Eight / The Kid
- Nadia Gray - Nadia Rokovsky, Number 8
- George Baker - The New Number Two
- George Coulouris - Man with the Stick
- Justine Lord - Sonia
- Mark Eden - Number One Hundred
- Conrad Phillips - Doctor
- Victor Maddern - Bandmaster
- George Benson - Labour Exchange Manager
- Zena Walker - Janet Portland
- Norma West - Girl Bo-Peep
- Denis Shaw - Shopkeeper
- Richard Wattis - Fotheringay
- John Castle - Number Twelve
- Joe Gladwin - Yorkshire Napoleon
- Clifford Evans - Number Two
- Thomas Heathcote - Lobo Man
- Peter Bowles - 'A'
- Earl Cameron - Supervisor
- Rosalie Crutchley - Queen
- André van Gyseghem - Retiring Number Two
- Aubrey Morris - Town Crier / Roman Emperor
- Gertan Klauber - Cafe Waiter
- Duncan Macrae - Doctor / Napoleon Bonaparte
- Sheila Allen - Number Fourteen
- Kevin Stoney - Colonel J.
- Richard Caldicot - Commander
- Valerie French - Kathy
- Fabia Drake - Welfare Worker
- Al Mancini - Announcer
- Michael Brennan - Killer Karminski
- Peter Wyngarde - Number Two
- Michael Bilton - M.C. Councillor
- Virginia Maskell - The Woman
- Terence Donovan - Sailor
- Annette Andre - Watchmaker's Daughter
- Lloyd Lamble - Stapleton
- Jane Merrow - Alison / Number Twenty-Four
- Basil Hoskins - Number Fourteen
- Keith Pyott - Waiter
- Alan White - Dutton
- George Pravda - Doctor
- Basil Dignam - Supervisor
- Brian Worth - Group Captain
- Guy Doleman - Number Two
- Katherine Kath - Engadine
- Finlay Currie - General
- Lucille Soong - Flower Girl
- Patrick Jordan - Danvers
- George Merritt - Postman
- Peter Howell - Professor
- Lockwood West - Camera Shop Manager
- John Cazabon - Umbrella Man
- John Cazabon - Man in Cave
- Martin Miller - Watchmaker / Number Fifty Four
- John Frawley - Flowerman
- Arthur White - Stall Holder
- Patsy Smart - Night Maid
- Patsy Smart - Waitress
- Oliver MacGreevy - Gardener / Electrician
- Patrick Cargill - Number Two
- Patrick Cargill - Thorpe
- Wanda Ventham - Computer Attendant
- Charles Lloyd Pack - Artist
- Mark Burns - Number Two's Assistant
- Angela Browne - Number Eighty-Six
- Barbara Yu Ling - Taxi Driver
- Stephanie Randall - Maid
- Lucy Griffiths - Lady in Corridor
- Lucy Griffiths - Judge
- Christopher Benjamin - Labour Exchange Manager
- Christopher Benjamin - Number Two's Assistant
- Christopher Benjamin - Potter
- Jack Allen - Doctor
- Frederick Piper - Ex-Admiral
- Georgina Cookson - Mrs. Butterworth / Number Two
- Georgina Cookson - Blonde Lady
- David Garfield - Hospital Attendant
- Keith Peacock - Guardian
- David Arlen - Karel
- Kenneth Griffith - The President
- Kenneth Griffith - Schnipps / Number Two
- Hilda Barry - No. 38
- Jack Le White - Judge
- Annette Carell - 'B'
- Bettine Le Beau - Maid
- Peter Brace - Guardian
- Peter Brace - Mechanic
- Terry Yorke - Thug
- Peter Brayham - Thug
- Rachel Herbert - Number Fifty Eight
- Grace Arnold - Number Thirty Six
- Grace Arnold - Maid
- Kenneth Benda - Supervisor
- Alf Joint - Mechanic
- Gay Cameron - Number Thirty-Six
- David Nettheim - Doctor
- Pat Keen - Nurse
- Dinny Powell - Guardian
- Betty McDowall - Professor's Wife
- Ian Fleming - Man at Cafe and First Top Hat
- Norman Mitchell - Mechanic
- Bette Bourne - Projection Operator
- Dennis Chinnery - Gunther
- Jon Laurimore - Ernst
- Niké Arrighi - Gypsy Girl
- Camilla Hasse - Day Supervisor
- Bill Cummings - Horseman
- Bill Cummings - Henchman
- Michael Nightingale - Night Supervisor
- Denise Buckley - Maid
- Gerry Crampton - Kosho Game Opponent
- Gerry Crampton - Guardian
- William Lyon Brown - Doctor
- Patricia Jessel - Psychiatrist
- Bee Duffell - Psychiatrist
- Victor Platt - Assistant Supervisor
- Shivaun O'Casey - Nurse
- Geoffrey Reed - Skipper
- Joe Dunne - Tower Guard
- Larry Taylor - Mexican Sam
- Larry Taylor - Gypsy Man
- Romo Gorrara - Tower Guard
- Michael Danvers-Walker - Painter
- Michael Danvers-Walker - New Man
- Michael Miller - Man in Buggy
- Michael Miller - Number Ninety-Three
- Hugo Schuster - Professor Jacob Seltzman / The Colonel
- John Wentworth - Sir Charles Portland
- James Bree - Villiers
- Harold Berens - Reporter
- Harold Berens - Boxing M.C.
- John Maxim - Number Eighty Six
- John Maxim - Judge
- Fredric Abbott - Potter
- Henry B. Longhurst - Old Guest
- John Nolan - Young Guest
- Jack Cooper - Corridor Guard
- Jack Cooper - Guardian
- Gordon Tanner - Town Elder
- George Leech - Corridor Guard
- George Leech - Guardian
- Michael Balfour - Will
- Gordon Sterne - Bystander
- Monti DeLyle - Town Dignitary
- Leslie Crawford - Gunman
- Frank Maher - Gunman
- Kathleen Breck - Number Forty-Two
- Bartlett Mullins - Committee Chairman
- June Ellis - Number Forty-Eight
- Michael Billington - Woodland Man
- John Hamblin - Woodland Man
- Joseph Cuby - Member of Social Group
- Michael Chow - Member of Social Group
- Norman Scace - Psychiatric Director
- Derek Aylward - New Supervisor
- Hilary Dwyer - Number Seventy-Three
- Max Faulkner - Scots Napoleon
- Max Faulkner - Horseman
- Arthur Gross - Control Room Operator
- Michael Segal - Laboratory Technician
- Margo Andrew - Shop Kiosk Girl
- Susan Sheers - Code Expert
- Fred Haggerty - Guardian
- Eddie Powell - Guardian
- Sheena Marshe - Barmaid
- John Rees - Welsh Napoleon
- John Drake - Bowler
- Ann Barrass - Technician
- Patrick McGoohan
- Rose Tobias Shaw
- David Tomblin
- Albert Elms
- Robert Farnon
- Wilfred Josephs
Frederick Piper interpreta a Ex-Admiral en la serie.
Earl Cameron interpreta a Supervisor en la serie.
Aubrey Morris interpreta a Town Crier / Roman Emperor en la serie.
Fenella Fielding interpreta a Loudspeaker Announcer en la serie.
Peter Swanwick interpreta a Supervisor en la serie.
Angelo Muscat interpreta a Le majordome en la serie.
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