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1 - 22 October 1977

Average Viewing Figure: 8.3M


The Doctor becomes infected with a sentient virus so clones of himself and Leela are injected into him to flush the enemy out



Tom Baker (The Doctor), Louise Jameson (Leela), Frederick Jaeger (Professor Marius), Michael Sheard (Lowe), Brian Grellis (Safran)

Edmund Pegge (Meeker), Jay Neill (Silvey), Anthony Rowlands (Crewman), Roy Herrick (Parsons), Elizabeth Norman (Marius' Nurse)

Nell Curran (Reception Nurse), John Leeson (Nucleus Voice/K-9 Voice), Jim McManus (Ophthalmologist), Roderick Smith (Cruikshank)

Kenneth Waller (Hedges), Pat Gorman (Medic), John Scott Martin (Nucleus)

Uncredited Cast

Stuart Myers, Harry Fielder (Crewmen), Alan Clements, Derek Hunt, Leslie Bates, Kenneth Sedd, Cy Town, Margot Gordon (Bi-Al Members)


Bob Baker, Dave Martin (Writers), Dudley Simpson (Incidental Music), Dick Mills (Special Sound), Norman Stewart (Production Assistant)

John Nathan-Turner (Production Unit Manager), Brian Clemett (Lighting), Michael McCarthy (Sound)

Ian Scoones, Tony Harding (Visual Effects Designers), Nick Allder (Film Cameraman), Raymond Hughes (Costume Designer)

Maureen Winslade (Make-Up Artist), Robert Holmes (Script Editor), Barry Newbery (Designer), Graham Williams (Producer)

Derrick Goodwin (Director)  

Uncredited Crew

Mat Irvine, Steve Bowman, Andy Lazell (Visual Effects Assistants)


Filming Locations

  • Television Centre: Studio 6

  • Bray Studios

Death the Constant Companion

  • Lowe [killed by K-9]

  • Safran [stabbed in the neck]

  • Meeker [stabbed in the back]

  • Silvey [shot and killed by Lowe]

  • Crewman [shot and killed]

  • Parsons [shot and killed by Lowe]

  • Cruikshank [shot and killed by K-9]

  • Ophthalmologist [shot and killed by K-9]

  • Hedges [shot and killed by K-9]

  • Medic [shot and killed by K-9]

  • Nucleus [destroyed along with the Titan Base]

  • Crewmen [shot and killed]

Number of Production Days: 5

Production Days

  • 12 Days between Tueday 22 March - Tuesday 26 April 1977

Production Errors

  1. The first model shot of the Bi-Al Foundation already has the damage caused by the shuttle crash later-on 

  2. An entire wall shakes when Lowe presses the distress button in his office

  3. The knife that Leela uses to kill Meeker wobbles back and forth after Meeker falls to the floor  

  4. Somebody can be seen moving at the back of the set at the beginning of episode two 

  5. A camera and crewmembers can be been reflected in Marinu's nurse head-mirror at one point 

  6. The shadow of a boom mic can be seen when The Doctor congratulates himself for blowing the Swarm up

  7. The clones of The Doctor and Leela should have been naked when created, and not wearing clothes 

  8. Professor Marius seems very content letting K-9 go, considering he sees the robot dog as his best friend 

  9. Several guns appear to have no triggers or holes in the barrel 

Working Titles

  • The Invisible Invader


The Invisible Enemy is one of those serials which look good on paper but not necessarily on-screen. The Invisible Enemy is another example which proves that the Baker-Martin duo continually provide storylines which just cannot be made on the restricted Doctor Who budget. A slow-moving first episode is followed by three more equally slow and tiresome episodes. There are good visuals but the main focus of the serial – travelling through The Doctor’s brain is seriously underwhelming. CSO takes dominance over constructed sets and whenever the two are mixed together the end result is rather disappointing. The Nucleus (one of the worst Monster ever in the show’s history) is very weak, taking over everyone it comes into contact. The Nucleus possess no credible threat considering the humans its possess have to help it move around the place. There was certainly a lot of potential here to create a dynamic story which explores the inner working of The Doctor's brain. Considering the story only gives ten minutes of The Doctor and Leela wondering inside The Doctor's brain there is very little reason to get excited about. Not bad. Just a big mess. **

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