Full Circle (Doctor Who)

Full Circle is the third serial of the 18th season of the British science fiction television series Doctor Who. Written by seventeen-year-old Andrew Smith and directed by Peter Grimwade, the serial was first broadcast in four weekly parts on BBC1 from 25 October to 15 November 1980. The serial sees the Fourth Doctor (Tom Baker) and his companions Romana and K9 inadvertently enter the smaller universe of E-Space, where they land on the lush forest planet Alzarius, during which an event called Mistfall causes amphibious Marshmen to rise from the water and threaten the humanoid Alzarians. The serial is the first regular appearance of the companion Adric (Matthew Waterhouse), a young orphan and mathematical prodigy among the Alzarians.

The outline for Full Circle was devised by Smith, a fan of the show who had previously submitted spec scripts to it. Upon becoming the show's script editor and discovering virtually no material for the upcoming season, Christopher H. Bidmead met with Smith and commissioned a script based on his outline. Peter Grimwade, who had experience with the show as a writer and production assistant, was chosen to direct the serial. Multiple effects were designed for the story, including spider props and aquatic costumes for the Marshmen. After three days of location filming at Black Park in Buckinghamshire, the rest of the serial was filmed in studio at the BBC Television Centre, which was complicated by Tom Baker's on-set behavior. Paddy Kingsland provided the incidental music for the serial, composing leitmotifs for several characters.

The news of Tom Baker's departure from the series led to heightened media attention to the show at the time the serial aired. Despite this, Full Circle aired to relatively low ratings, never exceeding 5.9 million viewers, partially due to competing with Buck Rogers in the 25th Century on ITV, but received a decent Appreciation Index score. The serial received mostly positive reviews from contemporary fans. Retrospective reviews have also been positive, with many praising Grimwade's direction and Baker's performance, as well as the design of the Marshmen. Critics have noted the serial's approach to the theory of evolution, the role of science and ritual in the story, and its themes of authority and colonization. The serial was novelised in 1982, and received an audio sequel from Big Finish Productions titled Mistfall.