While it’s very easy to spot patterns that aren’t there, I think there’s a definite sense of Season Eight leading up to this episode, and the next story. We hadn’t seen the TARDIS since Spearhead from Space, but it reappeared in Terror of the Autons, we got our first glimpse inside it since The War Games in the previous episode, and here, 39 episodes into his era, Jon Pertwee gets to pilot the Police Box for the first time. Fair enough, it’s only for a short trip, but at last the show is breaking out of the shackles of the exile format.

Baker and Martin (or, realistically, Terrance Dicks) give this an appropriate rationale – the Doctor needs the Master’s knowledge of dematerialisation theory to take off – and again there’s a sense that some care has been taken to set this up. Most of the episode is secondary to the big moment of the TARDIS dematerialising.

The Doctor’s elaborate deception to convince the Master to help him also feels like it’s been well set up with his attempt to escape using the Master’s dematerialisation circuit in Terror of the Autons, and his grumpiness about being stuck on Earth at the end of The Mind of Evil. Jo’s horrified reaction, the way she bangs on the TARDIS door begging him to stay, and then steps back to watch the Ship leave comes across as a similarly significant moment to the Master’s regeneration and TARDIS hijack at the end of Utopia. The fact that he’s still stuck at the end (Pertwee again overplaying a mildly amusing line as if it’s pure comedy gold) is by the by, in context the Doctor travelling in time and space is as significant as him discovering he is not the last of the Time Lords.

The rest of the episode is very well done: Michael Ferguson directs the three major action sequences very well: Jo and the Doctor’s escape from a convulsing Axos looks like a 1980s pop video with rotating heads and electronic effects; the attack on the UNIT convoy looks dynamic, and the final battle in the power room is suitably brutal and desperate. The script has a slightly giddy excitement to it, packed with big ideas that are almost casually thrown away: the fannish notion of the Doctor taking revenge against the High Council of the Time Lords and turning Axos into a TARDIS sounds like the plot of an EDA novel. Again, all that undermines it are performances that are vivid for the wrong reasons, as if some of the actors think unless they play it big and broad they’ll be lost in the mix.

Next episode: Colony in Space