White witch Olive Hawthorne warns that dark forces are stirring in the village of Devil's End, where the Master is posing as the new vicar. The Doctor learns that Professor Horner, an archaeologist, is planning to open an ancient barrow near the community. He and Jo race to stop Horner, but they are too late and bizarre energies are loosed. A stone gargoyle prowls Devil's End, doing the Master's evil bidding, while the Brigadier discovers that an impenetrable heat barrier surrounds the town. But the Doctor is convinced that these phenomena are just pretexts to the arrival of a being older than humanity itself...

Ever since reading Dennis Wheatley's 1935 novel The Devil Rides Out, Doctor Who producer Barry Letts had harboured an abiding interest in tales of black magic. As such, when he needed an audition piece for the roles of Jo Grant and Mike Yates in June 1970, he devised a scene in which Jo and Mike were confronted by the Devil in a church. Some time later, Letts decided that he should try his hand at writing a Doctor Who adventure himself. He already had some writing experience, including several Doctor Who storylines which had been rejected in late 1966. Although Letts wanted to incorporate the occult into his scripts, he felt that it paired poorly with Doctor Who's rational approach.

Script editor Terrance Dicks nonetheless encouraged Letts to expand upon his audition piece, observing that he could take the opportunity to explain magic in scientific terms. Letts decided to develop a back-up story which could air last in Doctor Who's eighth season, should problems arise with other scripts. However, Letts felt that he would benefit from collaborating with an experienced co-writer, and approached his friend Owen Holder, with whom he had scripted episodes of Skyport a decade earlier. When Holder proved unavailable, Letts' wife, Muriel, instead recommended Robert Sloman, who was a friend's husband. Although his prior writing experience was exclusively in plays, Sloman agreed to work with Letts on the project.

Barry Letts and Robert Sloman drew upon a recent BBC-sponsored dig at the Silbury Hill mound

Letts and Sloman took inspiration from the 1969 text Chariots Of The Gods?: Unsolved Mysteries Of The Past by Erich von Däniken, which proposed that aliens had visited Earth in prehistoric times. They also drew upon a recent BBC-sponsored dig at Silbury Hill, a mound near Avebury, Wiltshire with strong folkloric associations. These elements prompted the notion of a devil-like alien -- first called a Damon, then a Demon -- which had influenced humanity's development from an early stage. The alien dwelt within a burial mound called the Devil's Dyke, later amended to the Devil's Hump. Another possible name change involved the white witch, Olive Hawthorne, who may have been called Olivia Featherstone at one stage.

The storyline for “The Demons” was commissioned from Sloman on December 17th, and the scripts three weeks later, on January 6th, 1971. It was agreed that the serial would be credited to the pseudonym “Guy Leopold” (the first name being that of Sloman's son, and the surname coming from Letts' middle name). This was done, in part, to avoid upsetting the Writers' Guild by having a producer writing for his own show, and also because Sloman did not want to give the impression that his writing partnership with Laurence Dobie had dissolved. Like every story in Season Eight, “The Demons” featured the Master. By now, however, Letts was aware that having the character appear so regularly was a mistake. As a result, it was decided that the adventure would culminate in the Master's arrest by the United Nations Intelligence Taskforce (UNIT).

Letts and Sloman had to tread carefully in their handling of religious elements in “The Demons”. This resulted, for instance, in the relocation of the Master's rituals from the church itself to the crypt -- referred to exclusively as the “cavern” -- below. Similarly, a reference to the Devil as “the Horned God” was changed to “the Horned Beast”. Particularly contentious was the incantation chanted by the Master at his black sabbath; ideas such as having him give a reverse recitation of the Lord's Prayer or Eskimo Nell were considered, before Letts finally decided upon a backwards version of the nursery rhyme Mary Had A Little Lamb.

Letts wanted to use “The Demons” to expose more of the private lives of the UNIT team, such as by having Yates and Benton spend most of the serial out of uniform. To this end, Dicks suggested including a glimpse of the Brigadier's wife, whom he proposed might be called Fiona. However, Nicholas Courtney was not in favour of the idea, and it was excluded from the scripts. For the scene in which Jo got herself and the Doctor lost by holding a road map upside-down, Letts was inspired by a real incident when Jon Pertwee and Katy Manning were driving to a location shoot.

By early 1971, it was clear that “The Demons” would indeed be pressed into service as the fifth and final adventure of Season Eight. Letts originally hoped to direct the story himself, but ultimately secured the services of Christopher Barry, who had not worked on Doctor Who since The Power Of The Daleks almost five years earlier. It was Barry who asked that the story be retitled The Daemons, arguing that the archaic spelling lent additional atmosphere.

Letts felt that the serial was particularly conducive to location work, and made arrangements to trade a two-day studio block for a second week of pre-filming. All of the venues Barry chose were in Wiltshire, where production began on April 19th. Work on the first day got under way near Lambourn, where the Campbell Aircraft Company offered a suitable venue for the UNIT garage; the material at the crossroads was also recorded in the same vicinity. Later that day, cast and crew travelled to Knighton, where further roadside scenes were completed near Oaken Coppice.

The main location for The Daemons was the village of Aldbourne, which posed as Devil's End. Work there initially ran from April 20th to 22nd. Considerable use was made of the Church of St Michael, a local pub called the Blue Boar (dressed as the Cloven Hoof) and the nearby Four Barrows, which served as the Devil's Hump. Many Aldbourne residents participated in the recording, and virtually everyone involved would enjoy fond memories of their time in the community. On April 23rd, a disused airfield at Darrell's Farm in Ramsbury was used as the site of the heat barrier. The 24th was spent back at Aldbourne, with the Headington Quarry Men from Oxford playing the Morris dancers. Following a day off, Barry's team returned to Darrell's Farm on April 26th and 27th, and then Aldbourne from the 28th to the 30th.

With only three studio days for the five-part story, The Daemons eschewed the season's normal production pattern, which had consisted of fortnightly two-day blocks. Instead, recording took the form of three single-day sessions, each spaced roughly a week apart. The first of these occurred on May 11th at BBC Television Centre Studio 4 in White City, London. On this day, Episode One was completed alongside all of the remaining material for Episode Two, with the exception of scenes set in the vicarage and in the bedroom at the Cloven Hoof, as well as the Doctor's encounter with Bok. Nicholas Courtney was pressed into additional service as the voice of the BBC3 announcer.

Recording resumed on May 19th, again in TC4. Barry and his team completed the rest of Episodes Two and Three, as well as some Episode Four material. The latter included sequences in the bedroom, the vicarage and the UNIT mobile HQ -- to avoid having to erect those sets again the following week -- together with the scene where Benton and Miss Hawthorne heard the arrival of the Morris dancers. It was now Barry's turn to provide a vocal performance, as the RAF pilot.

Work on Doctor Who's eighth production block concluded on May 26th

Work on The Daemons -- and Doctor Who's eighth production block as a whole -- then concluded on May 26th in TC1, with the recording of the outstanding sequences from Episodes Four and Five. The original plan for Azal was to have Stephen Thorne provide the Daemon's physical presence, but mouth along to dialogue which had been pre-recorded by Anthony Jackson. However, it appears that this approach was deemed unsuccessful during rehearsals, and Thorne instead voiced Azal himself. Meanwhile, Roger Delgado paid tribute to guest star Damaris Hayman, who played Miss Hawthorne, by adding the phrase “namyah siramad” to the Master's backwards incantations.

The BBC's Saturday evening schedule changed throughout the broadcast of The Daemons. On May 22nd, Episode One was preceded by an extended edition of Grandstand (highlighted by an England versus Scotland football match) and an episode of The Pink Panther, as well as the usual news and weather. The following week, Walt Disney's Wonderful World Of Colour returned to the slot before the news update, but no Tom And Jerry cartoon short aired between The Daemons Episode Two and The Saturday Western. There was another extra-length Grandstand on June 12th, featuring the final of the Anglo-Italian football tournament; it led into the news and weather, and then The Daemons Episode Four.

Lastly, on June 19th, The Pink Panther and highlights from the 1971 Royal Tournament replaced the Disney programme prior to the transmission of the Doctor Who season finale. Amusingly, the climax of Episode Five shocked some viewers, who wrote letters condemning the BBC for blowing up a real church -- when, it fact, it was just a model, filmed on location.

• Doctor Who Magazine #241, 31st July 1996, “Archive: The Daemons” by Andrew Pixley, Panini UK Ltd.
• Doctor Who Magazine Special Edition #2, 5th September 2002, “Something Old, Something New” by Andrew Pixley, Panini Publishing Ltd.
• Doctor Who: The Complete History #17, 2015, “Story 59: The Daemons”, edited by John Ainsworth, 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.