‘While there’s life…’ I find it impossible to watch this dispassionately: there’s so much sadness wrapped around Tom’s departure – much more than in Pertwee’s, which felt more like the celebration of an era than a funeral – that the context of this episode overshadows the content.

As a farewell, I feel this ranks alongside The Tenth Planet 4 – the show’s linchpin figure is shuffled off by a production team eager to do something different. In his finale Troughton got to mount a robust defence of the good the second Doctor had done; Pertwee got to face his greatest vice and greatest fear and was reborn a new man. Tom gets to pull out a plug to – presumably – save the universe (one of the faults of this is that it’s not made entirely clear whether the Doctor has saved the day at the end – it’s almost as ambiguous as the end of The Armageddon Factor). I believe Baker hated the lack of a grand, heroic moment here – instead, it’s plastered with Ian Levine clips and shabby editing (the offscreen fall that happens at different speeds, the security guards that disappear between location and studio). By most objective measures, this is a mess, and a disservice to an actor who redefined the Doctor perhaps forever.

Other bits of the plot are as half-formed as the mysterious Watcher. Seeing him pilot the TARDIS is jarring. Having him revealed to be ‘the Doctor all the time’ is meant to confirm our suspicions – but what suspicions? What hints have we that this is the Doctor? Presumably, like a Cho-Je, he’s meant to be a hazy premonition of Peter Davison, present because the Master is ‘interfering with the law of cause and effect’. The outcome of the regeneration is there before the cause, and so the fourth Doctor must let go to put the universe back on track? Fans can read whatever they like into it because the script doesn’t think it needs saying.

And the Master’s plan changes from scene to scene depending on what helps move things forward. One moment, appalled by the Monitor’s disintegration, he’s fleeing Logopolis. The next he’s helping the Doctor. Then, out of nowhere, he’s hatched a plan involving a fake light-speed override. Then he’s decided to broadcast a message to the universe to make himself absolute ruler. What a mess.

But… It still hits me in the stomach, especially the moment when the Doctor peers through the blinds to see the Watcher, standing in the doorway of the TARDIS practically tapping his watch: this is Peter’s show now, old man. Move along. Tom’s desolate look as he turns back to face the little future he has left is gutting. I love the last instance of Season 18’s focus on the passage of time: the Doctor arrives at the Pharos Project at night and he dies at dawn (similarly, he arrived on Traken at night and the sun rises as he faces his destiny with Tremas, and Zolfa-Thura moves from day to night).

As Paddy Kingsland’s ethereal music plays, and Tom speaks his final lines it’s hard not to feel that some of that old, indefinable magic has been lost. And then Davison sits up and smiles, and, perhaps, there’s hope for some new magic. Well, that’s the end of that. But it’s probably the beginning of something completely different.

Next episode: Castrovalva