It is the year 1666, and the Great Plague is rampant throughout England. The Doctor, Adric, Nyssa and Tegan discover that aliens -- the Terileptils -- are operating in a small village. They have taken control of much of the local population and are driving away the rest using an android disguised as the Grim Reaper. With the help of unemployed thespian Richard Mace, the Doctor learns that the Terileptils intend to rid the Earth of humanity, and have amassed an army of plague-carrying rats to help them finish the deed.

During the gestation of Doctor Who's eighteenth season, producer John Nathan-Turner and script editor Christopher H Bidmead had been eager to recruit new writers to the programme. One name that was recommended to Bidmead was a radio playwright and author of short stories named Eric Saward. Saward had principally written thrillers such as Small Monet for the audio medium, but had never worked in television before. Nonetheless, Saward agreed to develop a proposal for Doctor Who.

Around the end of March 1980, Saward submitted a story idea bearing the intentionally ludicrous title of “Invasion Of The Plague Men”. This was inspired by the work of a former girlfriend of Saward's, who had been studying the architecture which arose in the wake of the Great Fire of London in September 1666. That disaster had followed close on the heels of another catastrophe in the same area, namely the 1665-1666 outbreak of what is generally believed to have been bubonic plague. Saward's girlfriend had observed that the black rats which carried the plague became virtually extinct within months of the Great Fire, and Saward thought that this would provide an effective science-fiction “hook” for a story about social conditions in mediaeval England. Saward also viewed “Invasion Of The Plague Men” as an opportunity to reuse the character of Richard Mace he had created for several radio plays during the mid-Seventies. Originally an actor and detective living in Victorian London, Saward now reimagined Mace as a thespian put out of work by the paranoia generated by the plague.

“Invasion Of The Plague Men” did not find favour with Nathan-Turner. He was concerned that it was too similar to 1977's The Talons Of Weng-Chiang, and felt that it was exactly the kind of whimsical Doctor Who adventure he was ardently trying to dispense with. In particular, Nathan-Turner was unimpressed with the inclusion of Richard Mace. As a result, there was no progress on Saward's submission until several months later, when Bidmead -- now in the process of leaving Doctor Who -- began turning his attention to Season Nineteen. It was decided that “Invasion Of The Plague Men” had enough potential that Saward should be given the opportunity to develop his ideas further. On September 23rd, he was commissioned to provide a detailed storyline, with the title now amended to simply “Plague Rats”.

Several changes now had to be made to Saward's original vision of the serial. It as now known that Tom Baker would be leaving Doctor Who, and so Saward had to account for the presence of an as-yet-unknown Fifth Doctor. Furthermore, the line-up of companions had expanded to include Adric and Tegan Jovanka, and at that time Nathan-Turner was also contemplating making Nyssa a regular character. Saward was able to make the necessary amendments to his storyline, and on November 20th was commissioned to write the full scripts.

Soon afterward, the still-lurid “Plague Rats” title was dispensed with, and Saward's serial became known as The Visitation. In preparing his episodes, Saward hewed to the broad strokes of recorded history concerning the Great Fire. Most notably, he made use of the conflagration's well-established origins in a bakery owned by Thomas Farriner (or Farynor) on Pudding Lane, beginning shortly after midnight on September 2nd, 1666.

One milestone that Nathan-Turner asked Saward to include in The Visitation was the destruction of the Doctor's sonic screwdriver. Like K-9, Nathan-Turner viewed the screwdriver -- which had featured in Doctor Who since Fury From The Deep in 1968 -- as an overly convenient plot device. He thought that doing away with it would challenge Doctor Who's scriptwriters to be more imaginative in devising ways for the Doctor to solve problems, and would also make the Time Lord seem less invulnerable to viewers. Nathan-Turner's new Doctor, Peter Davison, agreed with his producer: he felt that it would be more interesting if the Doctor instead carried an assortment of everyday objects in his pockets, and used these to help him get out of trouble.

Meanwhile, Nathan-Turner was searching for a new script editor to replace Bidmead, who would be finishing his one-year contract at the end of December. Bidmead himself suggested to Saward that he might consider applying for the position. Saward was interested in the job, but subsequently learned that Bidmead was being succeeded by Antony Root; it was Root who helped shepherd The Visitation to its finished form. Unbeknownst to Saward, however, Root's appointment was only for three months as a trainee. Although consideration was given to making him a permanent member of the production team, he had already agreed to a temporary posting on Juliet Bravo, and there was no guarantee that he would be able to return to Doctor Who. This left Nathan-Turner looking for another interim script editor, and Root suggested Saward, who had impressed him during the development of The Visitation. In February 1981, Nathan-Turner contacted a surprised Saward with the offer of a three-month contract, and Saward agreed.

By the time Saward joined the production team in mid-April, Season Nineteen was already undergoing a degree of upheaval. The original premiere adventure, “Project Zeta-Sigma”, had been abandoned at a late date, forcing a rearrangement of the recording schedule. The Visitation was intended to air later in Season Nineteen, but it was decided that it should be the second story into production, after Four To Doomsday. Its position in the transmission order would remain the same, however: Nathan-Turner had now decided that he wanted give Davison several stories to become accustomed to the role of the Doctor before recording his debut adventure (which would now be Bidmead's own Castrovalva). As a result, The Visitation became Serial 5X, and would be directed by Peter Moffatt, whose last work had been on State Of Decay a year earlier.

Production of The Visitation began on May 1st at the Ealing Television Film Studios, where material on Pudding Lane and in the Bakery's oven room was recorded. This was followed by three days at Black Park in Fulmer, Buckinghamshire from May 5th to 7th, where all of the scenes in the forest were shot. Unfortunately, cast and crew found themselves filming below a Heathrow Airport flight path, and the noise of approaching aircraft regularly disrupted recording. On the 7th, however, an air traffic controller's strike put an end to these disturbances, and Moffatt and his team were able to make up for the time they had previously lost.

Included in these sequences was the debut of the main Terileptil costume, which incorporated remote-control animatronics to control the alien's lips and gills. This was the first time such technology had been used in Doctor Who; it was conceived by visual effects designer Peter Wragg and constructed by Richard Gregory of Imagineering. Although the Terileptil costume was very expensive, Nathan-Turner was eager to combat the perception that Doctor Who monsters often looked like pantomime horses when they spoke.

On May 8th, a final location day took the production to a manor house called the Tithe Barn in Hurley, Berkshire. This served as the exterior of the Squire's residence. Studio recording then began with a two-day session in BBC Television Centre Studio 3. Taking place on May 20th and 21st, the block's first day dealt with scenes in the stable and the Terileptil escape pod, while the second day concentrated on the TARDIS sequences, along with those in the Pudding Lane bakery and Mace's barn.

Recording continued in TC3 for the second session, which ran from June 3rd to 5th. These days were devoted to material in the manor house, although the opening TARDIS scene was remounted on the final day of recording after Nathan-Turner reacted negatively to the original version. With The Visitation completed, there was then an almost two-month hiatus before work on Season Nineteen could resume. This was scheduled to enable Davison to record the second season of his sitcom Sink Or Swim, and marked the first time that such a lengthy pause had ever occurred in the middle of a Doctor Who production block.

• Doctor Who: The Handbook: The Fifth Doctor by David J Howe and Stephen James Walker (1995), Virgin Publishing, ISBN 0 426 20458 9.
• Doctor Who: The Eighties by David J Howe, Mark Stammers and Stephen James Walker (1996), Virgin Publishing, ISBN 1 85227 680 0.
• Doctor Who Magazine #275, 10th March 1999, “Archive: The Visitation” by Andrew Pixley, Panini UK Ltd.
• Doctor Who Magazine Special Edition #1, 2001, “Prince Charming” by Andrew Pixley, Panini Publishing Ltd.
• In-Vision #58, June 1995, “Production” edited by Anthony Brown, Cybermark Services.