With the Doctor once again free to wander in time and space, the TARDIS lands aboard the cargo ship SS Bernice. Jo believes that it is 1926, but the Doctor realises that the vessel is one which history records as having disappeared without a trace. The mystery deepens when a dinosaur attacks the Bernice -- after which the passengers and crew obliviously start to repeat their recent actions. The Doctor discovers that the ship is trapped inside a Miniscope: outlawed technology owned by a travelling showman named Vorg. But the Miniscope also houses the monstrous Drashigs, who threaten the lives of all those imprisoned within.

With Robert Holmes having delivered the premiere adventures for Doctor Who's seventh and eighth seasons -- Spearhead From Space and Terror Of The Autons, respectively -- script editor Terrance Dicks was eager for him to write for the programme again. On May 6th, 1971, Holmes was commissioned to write a storyline initially called “The Labyrinth”, and then “Out Of The Labyrinth”. It was constructed with the limitations of the Doctor Who budget very much in mind: not only could it potentially be made without location filming, but the action was evenly split between two locations with distinct sets of characters. This meant that members of the guest cast would only need to be hired for one of the two studio recording blocks.

Dicks' response to the “Out Of The Labyrinth” storyline was delayed by work on Doctor Who's ninth season, but Holmes was finally commissioned to write the scripts on November 24th. Soon thereafter, the serial was retitled “Peepshow”. At this stage, Holmes added the subplot about the attempted overthrow of President Zarb; Dicks was concerned that, as the story was originally structured, the only real threat facing Vorg and Shirna was the penalty for breaking import regulations. Inter Minor was named Odron for a time, and it was thought that the planet might host a convention of showmen. Pletrac was originally called Pletrac 4, while Orum, Kalik and the unseen Zarb were named Grig 07, X10 and X8, respectively. For a long time, the Miniscope was known as the Strobe. The name Drashig, meanwhile, was an anagram of “dish rag”.

With ambitious plans for Doctor Who's milestone tenth season, the budget-conscious “Peepshow” was a natural addition

Early in 1972, the BBC confirmed that Doctor Who would continue into a tenth season. Cognisant of the milestone, Dicks and producer Barry Letts began drawing up ambitious plans for the year's stories. As such, the budget-conscious “Peepshow” was a natural addition to the schedule to help balance the books, and it was placed second in the running order. Letts and Dicks planned to begin the year with a serial featuring all three actors to have played the Doctor: Jon Pertwee, Patrick Troughton and William Hartnell. With Troughton's schedule uncertain, it was decided that “Peepshow” should be made at the end of Doctor Who's ninth recording block, giving the production team more flexibility when it came to taping the multi-Doctor adventure. The practice of holding back one or more serials for the subsequent season had been typical for Doctor Who until 1968, but had so far been abandoned during the Pertwee era.

Pertwee was booked for all twenty-six episodes of Season Ten on February 9th. The next day, Katy Manning's contract was extended for at least twenty-two episodes. Meanwhile, Letts decided to invoke a clause he had negotiated when he became Doctor Who's producer, which permitted him to direct one story per year. Having handled Terror Of The Autons for the 1971 run, he would now take the reins of “Peepshow”. As John Andrews, Letts cast Ian Marter, whom he had offered the role of Mike Yates in 1970 until availability became an insurmountable issue. Likewise, Jenny McCracken and Cheryl Hall had both been contenders to play Jo Grant; they would now portray Claire Daly and Shirna, respectively. As Major Daly, Pertwee recommended his friend and The Navy Lark co-star Tenniel Evans. It was Evans who had originally encouraged Pertwee to consider playing the Doctor, and the leading man now repaid the favour.

Although it had been suggested at an early stage that “Peepshow” might be made entirely within the studio, it was ultimately allocated four days on location. The first venue was a stretch of the Tillingham Marshes on Howe Farm at Tillingham, Essex, which was used for the Drashig environment within the Miniscope. Work there spanned May 30th and 31st, with part of the second day also spent at the Carwoods Quarry in Asheldham, Essex for material at the cave mouth.

On June 1st and 2nd, cast and crew boarded the RFA Robert Dundas at Chatham, Kent. The vessel, which had been launched in 1938 and finally decommissioned in December 1971, posed as the SS Bernice. The Robert Dundas spent part of the first day travelling along the River Medway to Sheerness, Kent, but was otherwise docked during production. At one point, the shoot was interrupted when it was discovered that an old brass ship's compass had disappeared. The culprit turned out to be none other than Jon Pertwee, who had mistakenly believed that the compass was to be scrapped along with the Robert Dundas, and therefore wouldn't be missed. In fact, it was to be auctioned off along with other ship artifacts and, after learning of his error, an embarrassed Pertwee duly returned it.

Around the time that studio recording began for the serial, it was renamed Carnival Of Monsters, drawing upon some of Vorg's dialogue from Episode One. The change was made by Dicks, who worried that “Peepshow” had lewd connotations; Holmes was unhappy with this decision. As usual, the serial was taped in fortnightly two-day studio blocks, with the recording days occurring on Mondays and Tuesdays, as had been the case for most of Season Nine. Letts opted to take advantage of the adventure's bipartite structure to divide his studio sessions by setting.

As such, the first block -- on June 19th and 20th at BBC Television Centre Studio 4 in White City, London -- was used for all of the scenes which took place aboard the SS Bernice and inside the Miniscope workings. The Monday was devoted to Episodes One and Two, and the Tuesday to Episodes Three and Four. The scene in which the Doctor and Jo explored the hold gave Katy Manning a chance to perform her chicken impression, which she had taught herself as a child. Work on the 20th was interrupted by a bomb scare, although it transpired that this had been incited by the ticking of an alarm clock, stowed in a bag belonging to one of the effects assistants.

The second studio block, on July 3rd and 4th in TC6, concentrated on material set on Inter Minor, with the action taking place in what the script named the Vol-Dome. As with the first session, sequences from the first half of the story were taped on the Monday, and those from the latter half on the Tuesday; as such, neither Pertwee nor Manning was needed on the 3rd. Scenes in the Drashig cave for the two middle installments were also completed on the 4th. Holmes scripted authentic Polari for Leslie Dwyer to utter as Vorg in Episode Four, and both Pertwee and Dwyer delighted in showing off their extensive knowledge of the carny lingo. The actors playing the Inter Minor officials -- Peter Halliday, Michael Wisher and Terence Lodge -- were originally supposed to have their faces hidden behind masks. However, Letts decided to dispense with them, since he thought the performances would benefit from a full range of facial expression. Unfortunately, the headpieces worn by Halliday, Wisher and Lodge began to detach as work proceeded on the 4th.

The original cliffhanger for Episode 3 involved the Doctor being attacked by a Drashig and falling down a shaft

In post-production, both Episodes Two and Four were found to be significantly overlong, which forced a number of scenes to be trimmed throughout Carnival Of Monsters, and others to be moved to a different point in the narrative. Material involving Vorg, Shirna and the Inter Minor officials was a particular target. The climax of Episode Three was also completely rearranged. Originally, the cliffhanger involved the Doctor being attacked by a Drashig inside the Miniscope and falling down a shaft. At the start of Episode Four, the Drashig plummeted after him to its death, while the Doctor was seen to have been saved by catching his foot in a rope. As broadcast, this sequence was omitted altogether, although the dead Drashig still appeared. Instead, the Doctor's emergence from the Miniscope -- which, as scripted, occurred during Episode Four -- was brought forward to serve as the new cliffhanger.

Another late change involved the Doctor Who theme music. Delia Derbyshire of the BBC Radiophonic Workshop had originally arranged Ron Grainer's composition in 1963, and had made some alterations in 1967. Now, however, Letts requested a completely new approach which emphasised a more modern, electronic sound. The task was assigned to Paddy Kingsland of the Radiophonic Workshop, who created the new version on a synthesizer dubbed the “Delaware” -- a reference to the location of the Workshop on Delaware Road in Maida Vale, London. Kingsland was assisted by Derbyshire and their colleague, Brian Hodgson, who regularly provided special sound for Doctor Who.

The so-called “Delaware theme” was duly added to both Carnival Of Monsters and the next serial in production, Frontier In Space. A few weeks before Season Ten was scheduled to air, however, Letts began to have second thoughts. When Ronnie Marsh, the BBC's Head of Serials, voiced his unhappiness with the new arrangement, it was enough to convince Letts to abandon Kingsland's version and reinstate Derbyshire's. He subsequently learned that neither Derbyshire nor Hodgson particularly liked the “Delaware theme”, either. However, an early edit of Episode Two which featured Kingsland's arrangement was inadvertently made available to the Australian Broadcasting Commission, who screened it in 1978.

• Doctor Who Magazine Winter Special 1994, “Archive: Carnival Of Monsters” by Andrew Pixley, Marvel Comics UK Ltd.
• Doctor Who Magazine Special Edition #2, 5th September 2002, “Saturday Night's Alright For Fighting” by Andrew Pixley, Panini Publishing Ltd.
• Doctor Who: The Complete History #19, 2017, “Story 66: Carnival Of Monsters”, edited by Mark Wright, Hachette Partworks Ltd.
• Doctor Who: The Handbook: The Third Doctor by David J Howe and Stephen James Walker (1996), Virgin Publishing.
• Doctor Who: The Seventies by David J Howe, Mark Stammers and Stephen James Walker (1994), Virgin Publishing.