Derek Deadman is no Kevin Lindsay. He whispers like an Ice Warrior and sounds like Ian Dury (cue laboured Ian Stor-y and the Potato Heads’ Hit Me With Your Swagger Stick joke). The Sontarans are generally a good choice for this though, having assessed Gallifrey’s military potential as far back as The Time Warrior and, with their endless clone army, being a more credibly formidable threat than the Cybermen, and a more thuggish contrast to the genteel Time Lords than the Daleks. This lot look suitably robust and solid as they march through the Capitol.

I’m more perplexed by the is-he or isn’t-he sub-plot with Borusa though. I thought we’d established that Borusa was an ally, but this spends a lot of time casting doubt on whether he’s going to shoot the Doctor or not (despite him explicitly saying he’s carrying the gun in case the Doctor is being coerced). I guess it’s meant to be him uncertain whether the Doctor is his own master or not, and whether the Doctor becoming ‘the first President since Rassilon to hold the Great Key’ is simply a ploy by the Vardans and/or Sontarans to gain mastery over time. If so, they could have done with spelling it out a bit more clearly.

In general, though I enjoy the twist, this episode feels almost as improvised and desperate as the Doctor’s plan. A lot is made of the Doctor hiding his identity from the Sontarans, for about two scenes until the Castellan spills the beans – but it didn’t really matter. But it’s full of wonderful moments. I love Tom’s absolutely straight playing of his one-to-one with Borusa where they discuss the Chancellor’s Time Lordly detachment. I love Rodan doing her Romana audition piece and getting the Doctor to hand her tools. I love the Doctor’s absolute trust in Leela, and Leela’s delight in it. I love lines like ‘[The Vardans] had their uses’ and ‘They could rampage right through the whole universe. And not just this universe, all the universes’. The ambition and scale of the story carry this through even when some of the details aren’t quite right.

Next episode: The Invasion of Time – Part Six