The TARDIS brings the Doctor, Tegan and Turlough to the castle of Ranulf Fitzwilliam, in 1215 England. Also present are King John and his champion, Sir Gilles Estram, who have accused Ranulf of failure to provide adequate financial support to the throne. The Doctor is baffled -- not just because King John is meant to be in London, involved in the events which will lead to the signing of the Magna Carta, but also because he is strangely unperturbed by the arrival of the TARDIS. Soon the evidence mounts that the king is an impostor. But who is really pulling the strings, and to what end?

During 1981, Richard Gregory was involved with several Doctor Who serials through Imagineering, a freelance props company based in Witney, Oxfordshire. In November, Gregory approached producer John Nathan-Turner about a project developed by computer whizz Chris Padmore, owner of CP Cybernetics. He and software designer Mike Power had devised a working robot, with a body that could move in an approximation of a human's and which could mime speech to prerecorded dialogue. Work on perfecting a system which would enable the android to walk was also under way. Unfortunately, Padmore had run out of money, and efforts to secure additional funding -- both from the commercial sector as an advertising gimmick, and through a possible involvement in the science-fiction movie Xtro -- had come to naught. Padmore had then contacted Gregory, who suggested that the robot might find a use on Doctor Who.

Nathan-Turner was intrigued by the pitch and, in late November, he and script editor Eric Saward were given a demonstration of the prototype by Gregory and Padmore. The Doctor Who team was impressed, sensing that the android might appeal to the public in the same way as the robot dog K·9 four years earlier. They agreed that the waters should be tested in a short adventure; if this proved successful, the android might become a regular companion for the Doctor.

At Christmas 1981, John Nathan-Turner formally agreed to the use of the robot, on the condition that Chris Padmore continued to improve it

To write this introductory story, Nathan-Turner favoured television veteran Terence Dudley. In the last year, Dudley had scripted Four To Doomsday and Black Orchid for Doctor Who, plus A Girl's Best Friend, the pilot episode for the unsuccessful K·9 And Company spin-off. Saward argued against this choice: he was not impressed with Dudley's work, and the two men did not get along. Nonetheless, Nathan-Turner forged ahead, and a second demonstration of the android was arranged for Dudley's benefit around Christmastime. At this point, Nathan-Turner formally agreed to the use of the robot, on the condition that Padmore continue to improve it. In particular, the producer wanted the android to be more mobile, and he hoped that the walking mechanism would be functional by the time it went before the cameras.

In addition to the android's debut, Dudley was told that his narrative should feature the return of the Master. Anthony Ainley had been contracted to appear in one serial during Season Twenty -- although Nathan-Turner had originally envisaged the Master appearing in two stories per year -- but no suitable adventure had yet presented itself. Now Nathan-Turner felt that pairing the Master with the android would be an interesting new way to use the villain. Again, Saward disagreed with his producer: he felt that the Master was an inferior character, and was not eager to bring him back every year.

With these requirements in mind, Dudley resurrected an idea he had been contemplating prior to writing Black Orchid, which would take the TARDIS to the England of King John. In particular, the narrative would be set around the signing of the Magna Carta, the agreement between the English monarchy and rebellious barons which would limit the power of the throne. Although the Magna Carta was almost immediately violated and was quickly voided by Pope Innocent III, many of its provisions would later be restored, and form the basis of modern freedoms and liberties.

Into this scenario, Dudley introduced the Master, who would be operating under the alias of Sir Gilles Estram -- the surname being an anagram of “Master”. Keeping in mind the robot's limitations, Dudley decided to make it a shape-shifter, so that an actor could play the role as necessary; it was also Dudley who coined the name Kamelion. On February 22nd, 1982, Dudley was commissioned to write “The Android”. His scripts apparently went through several other working titles -- including “The Demons”, “A Knight's Tale” and, according to some publicity photos, “Demons Keeper” -- before becoming known as The King's Demons.

The Radio Times would list Sir Gilles as being played by “James Stoker” -- an anagram of “Master's joke”

The King's Demons was intended to be the penultimate story of Season Twenty, both in terms of production and broadcast. It would be the first assignment for young director Tony Virgo, making his only contribution to Doctor Who. It was Nathan-Turner, however, who recruited television veteran Gerald Flood to play King John and provide the voice of Kamelion. Meanwhile, it was decided to mask the Master's involvement in The King's Demons by having the Radio Times list Sir Gilles as being played by “James Stoker” -- an anagram of “Master's joke”.

As work began on The King's Demons, a pall hung over Doctor Who, and indeed the BBC as a whole. The electricians' union had been threatening strike action for weeks, and the picket lines finally went up in early November. As a result, Enlightenment -- the story which immediately preceded The King's Demons -- was suspended in mid-production, its pre-filming having been completed but its studio dates indefinitely postponed. Concern now arose that both The King's Demons and “The Return”, the Dalek story intended to close the season, would have to be abandoned.

Fortunately, the industrial dispute was resolved in late November. Nathan-Turner decided to preserve the original recording dates for The King's Demons to avoid the expense of extending the contracts of those involved. However, it was too late to completely salvage the season: Enlightenment would have to be finished during the studio dates originally meant for “The Return”, while the Dalek story would be delayed to Season Twenty-One, becoming Resurrection Of The Daleks. Consequently, The King's Demons would now serve as the season finale. As scripted, it ended with a cliffhanger leading into “The Return”, in which the TARDIS became trapped in a time corridor; Tegan asked if this was the Master's doing, but the Doctor suspected an even more malign force at work. Saward replaced this sequence with one which foreshadowed the Doctor's trip to the idyllic Eye of Orion -- a reference to the opening scenes of The Five Doctors, a twentieth-anniversary special being prepared for transmission in November 1983.

Dudley's script described The King's Demons as being set at Odiham Castle, near Basingstoke in Hampshire. This was based on historical fact: it was from either Odiham or Windsor Castle that King John departed for Runnymede, where the Magna Carta was signed. However, Odiham Castle had fallen into ruins by the start of the seventeenth century, with only a section of the octagonal keep still standing. Instead, Virgo took his team to Bodiam Castle, at Bodiam in East Sussex, which was the nearest castle to London in serviceable condition. Originally built by Sir Edward Dalyngrigge in 1385, it underwent a series of restorations beginning in the mid-nineteenth century, and was now owned by the National Trust. Work within Bodiam Castle and on its grounds took place from December 5th to 7th.

Meanwhile, the production team was having second thoughts about the viability of the Kamelion prop. Sadly, Mike Power had been killed in a boating accident, and no one else possessed the necessary understanding of the software which drove the android. As a result, Padmore had been unable to perfect the walking mechanism, and it took weeks to program all of the dialogue. It became clear that Kamelion could not be retained as a regular member of the TARDIS crew, and Nathan-Turner decided that he would be brought back for just one more story -- to air sometime during Season Twenty-One -- in which he would be written out of Doctor Who.

The single studio block allocated to The King's Demons took place on December 19th and 20th, at BBC Television Centre Studio 1 in White City, London. The sets for the Great Hall and the dungeon were used on both days, with scenes in the guest chamber and the dungeon corridor taped on the first day, and material in the Doctor's TARDIS, the Master's TARDIS, and the King's chamber and its adjacent hallway on the second day.

Unfortunately, the issues with Kamelion proved to be even more severe than anticipated. The prop constantly broke down, and it proved unable to maintain synchronisation with Flood's prerecorded dialogue. Virgo completed as much footage as he could, but several Kamelion scenes, as well as a number of sequences involving Tegan alone in the TARDIS, could not be finished by the end of the block. Happily, Nathan-Turner was able to schedule an extra day for The King's Demons in TC1 on January 16th, 1983, immediately before Enlightenment belatedly began its first studio session. The outstanding material in the King's chamber and the TARDIS was completed, with Kamelion working better than it had in December.

The broadcast of The King's Demons Episode Two on March 16th marked the end of Terence Dudley's involvement with Doctor Who. It also brought Season Twenty to a premature conclusion. Both the Tuesday and Wednesday timeslots would subsequently be occupied by the soap opera Triangle. This had been an uneven year for Doctor Who, with audience figures down sharply compared to Season Nineteen. Indeed, at times, the number of viewers had dropped to about the same levels which had provoked such concern during Season Eighteen, and provided some of the impetus for shifting Doctor Who from Saturday evenings to weekday nights.

• Doctor Who Magazine #269, 23rd September 1998, “Archive: The King's Demons” by Andrew Pixley, Marvel Comics UK Ltd.
• Doctor Who Magazine Special Edition #1, 2001, “Diamond Life” by Andrew Pixley, Panini Publishing Ltd.
• Doctor Who: The Complete History #37, 2017, “Story 128: The King's Demons”, edited by John Ainsworth, Hachette Partworks Ltd.
• Doctor Who: The Eighties by David J Howe, Mark Stammers and Stephen James Walker (1996), Virgin Publishing.
• Doctor Who: The Handbook: The Fifth Doctor by David J Howe and Stephen James Walker (1995), Virgin Publishing.
• In·Vision #68, November 1996, “Production” edited by Anthony Brown, Cybermark Services.