First broadcast 5 January 1982.

The TARDIS is locked into a course for the Big Bang at the behest of the Master (Anthony Ainley), who has kidnapped and imprisoned Adric (Matthew Waterhouse). While the Doctor (Peter Davison) continues to recover, Tegan (Janet Fielding) and Nyssa (Sarah Sutton) struggle to save the TARDIS from disaster.

Season 19 of Doctor Who brings in a phenomenon that will to one degree or another plague the series for the next seven seasons, which is the replacement of clothes with uniforms. Previous iterations of the series had seen the regular cast change their outfits from one serial to another – originally to blend into historical settings, but later as a simple nod to reality. While Hartnell and Troughton’s Doctors by-and-large wore the same costume in every serial, Pertwee and Baker wore a variety of outfits based on common themes. With “Castrovalva” (actually, since “The Keeper of Traken” the previous season) the regular characters – the Doctor, Tegan, Nyssa, and Adric – wear the same clothes for the duration of the season. In Tegan’s case it is a literally uniform, as she spends the start of each serial genuinely expecting the TARDIS to drop her off at Heathrow Airport. This loss of realism does genuinely damage the series a little, and it makes the various Season 19 characters a little more difficult to treat seriously than their predecessors. Goodness but they must smell something awful by the end of “Time-Flight” Part 4.

The end of the episode does at least get the serial outside of the TARDIS, with Tegan and Nyssa taking the Doctor to the alien village of Castrovalva to finish his recovery. The exterior scenes, shot in woodlands on 16mm film, really do lift the visual aspects of the episode. Director Fiona Cumming seems particularly adept at these scenes compared to the relatively static ones shot at BBC Television Centre.

It is not a great episode for either the Master – stuck cackling at a monitor screen – or Adric – laced up in an unedifying torture device, but at least Nyssa and Tegan get some time to work together. The characters were thrown together without time for introductions in “Logopolis”, and with Adric out of action it’s a valuable opportunity to let them bond. The episode in general sort of just sits there: what activity occurs feels a little too much like the previous instalment, and entire episodes running around white TARDIS corridors is rarely very interesting.