‘You have returned to us Doctor. Your travels are over.’ The final episode of the story, the Troughton years and the 1960s ties up the series as neatly as An Unearthly Child introduced it, 253 episodes ago. It all began with the Doctor declaring himself an exile, and promising one day he would get back. This is the day. And it ends with him exiled again, back to where he started: Earth, in the 20th Century.

Obviously there was no intention to stop the show here, and as a series finale this would be incredibly downbeat (they’d surely have ended it with the Doctor winning his freedom in a rather less qualified way). As a eulogy for the 1960s concept of the show, it’s quite stirring. The newly-recorded sequences of the ‘evils’ the Doctor has fought are well done, a nice recap of some of his most memorable adventures and The Dominators. And the Doctor’s defence of his own motives against the indolence of the Time Lords is great.

But the trial itself only occupies a couple of minutes in an episode that’s fairly shapeless. The desperate escape attempt in the TARDIS is meant to demonstrate the Time Lords’ great power and ability to reach across time and space to control it, but after two seasons that saw the Ship hijacked in space, reduced to a cupboard, penetrated by an alien intelligence, and exploded, it was never quite the safe haven we now think of it being. And this is followed by two more failed escape attempts, one engineered by the War Lord’s people and the other, somewhat half-heartedly, by Jamie and Zoe. The episode is practically the last word on capture/escape.

The really impressive thing about the episode is the introduction of the Time Lords, who never again achieve the Olympian detachment on display here. The point of the capture/escape routines are to demonstrate without doubt that there is no resisting the Time Lords: they can do practically anything they like, and choose not to. They’re terribly nice about it, but they are terrifying: they condemn an entire planet to imprisonment forever; they steal Jamie and Zoe’s memories of their adventures; they wipe the War Lord from history, and they execute capital punishment on the second Doctor.

In between all of this, the Doctor reveals the truth behind stealing a TARDIS and fleeing his own people: he was bored. It’s exactly the kind of bathetic revelation this needed, and which none of the mad fan theories of 49th Century Time Wars, mysterious Others, Timeless Children or half-human princelings can ever live down to. 750 years of excruciating boredom and inertia on the planet of sanctimonious autocrats is much more compelling. The point of the show is the Doctor’s adventures, not the Doctor’s origin story – it’s a show about moving forward and making a difference, not noodling on the past.

As the epilogue to the longest serial since The Daleks’ Master Plan, this is… ok. The real story ended last week, and this just ties up the loose end of the trial of the War Lord. The arrival of his guards in a SIDRAT, just like in Episode Eight, suggests this could go on for another fortnight. However, as the Time Lords are omnipotent the kind of constantly shifting balances of power in the last nine weeks can’t work: the scales are all in Gallifrey’s favour and the war plot is neatly concluded in plenty of time to refocus on the second Doctor’s own reckoning.

As a farewell for Troughton – it’s better than The Tenth Planet 4 by dint of actually giving him anything to do. But by its nature, this doesn’t allow him a final glorious triumph – it’s about the Doctor’s fall. True, he manages to argue his way out of being locked up in the Cloisters, but he loses his friends, his freedom and his face. The final sequence of Troughton gurning into oblivion, yelling no (just as the War Lord did about 15 minutes earlier) is as disconcerting and more horrible than Hartnell’s frighteningly weird final moments, and for the first time finishes a season on a decidedly uncertain note. My favourite moment of the episode comes near the start, when Zoe blurts out, ‘But you’ve helped people Doctor’ as though that justifies everything. And, as the judgment of the Time Lords shows, she was right.

Next episode: Spearhead from Space