‘What worries me is the level of coincidence in all this. Almost as if some cosmic influence…’ Grimwade at least makes some effort to imply someone is trying to direct these events – perhaps a hint that the White Guardian is working behind the scenes to provide the Doctor with allies against his counterpart (maybe you could ret-con the whole of the first part of Season 20 to the White Guardian’s interventions – reuniting the Doctor and Tegan, and freeing Tegan from the Mara before pitching them into a battle against darkness). Or maybe it’s just a cheap hand wave to excuse the second accidental reunion this series.

Whatever, the Doctor’s reaction to re-meeting the Brigadier is very sweet: Davison says the Brig’s full name as if he delights in it, and grins happily as the old warhorse huffs and snorts through their first conversation. Grimwade also gives a sort-of explanation why the 1983 Brigadier is out of sorts (and therefore, perhaps, more florid than usual) – a kind of nervous breakdown that has left him amnesiac (mention of Liz Shaw brings the memories flooding back via one of this era of the show’s beloved clip sequences).

Grimwade fairly deftly handles the transitions between 1983 and 1977: the “present” Brigadier remembers meeting Tegan, just before we see her meet the “past” Brigadier (in a strong dual performance from Courtney, the “past” version is stiffer and more like the old Lethbridge-Stewart, and he has a moustache). Exposition is delivered in both time zones, showing conversations and events (like the Doctor telling the “present” Brigadier that the wounded man in the TARDIS isn’t him) from the two perspectives. Even if the notion of a story taking place across multiple time zones is less uncommon than I used to think (City of Death, Warriors’ Gate, Earthshock and Time-Flight just in the last few seasons), it’s neatly introduced.

The downsides to the episode are that Turlough has quickly been sidelined – even in his first serial, there’s a sense there’s not enough story for him. He gets one decent scene with Angus Mackay (being very low-key creepy as a demon headmaster) and Valentine Dyall. The other is Mawdryn, who has to explain who he is and what his plot is directly to the audience because Grimwade’s hit the halfway point and forgotten to introduce his antagonist (‘The Time Lords abandoned us. Perpetual torment and despair. But the ending will come soon. I, Mawdryn, shall be a Time Lord.’). Much as I like the idea of Tegan and Nyssa being taken in by a fake regeneration of the Doctor, this isn’t the vehicle to try this on top of two time zones and a Black Guardian masterplan. The result is it’s introduced and then thrown away within a few minutes. We end the episode with the regulars having not actually learned very much themselves, and the audience waiting for them to catch up.

Next episode: Mawdryn Undead – Part Three