The irony is that the last extant William Hartnell episode doesn’t feature Hartnell – who was off sick. As such, the Doctor keels over just at the point that the Cyberman invasion fleet has appeared on the scanners. This at least makes the two events somehow seem connected, and foreshadows the forthcoming changeover: ‘I don’t understand it. He just seems to be worn out,’ says Polly.

What could it be that’s taken down the Doctor? Although the arrival of more Cybermen is clearly a danger, the approach of their planet is the bigger threat. ‘The Earth is being drained of it’s energy by this so-called planet Mondas or whatever it’s called,’ growls General Cutler. ‘To make matters worse, the energy drain is increasing rapidly,’ reiterates Secretary Wigner of International Space Command. Then there’s this exchange:

BEN: The Doctor said that it’s not only Earth that’s in danger but that Mondas itself is in far greater danger. Otherwise why have they bothered coming here?
CUTLER: And just how did he figure that out? It’s draining energy from the Earth, isn’t it?
BEN: Yes, but he said eventually it would absorb too much energy and burn itself out. Well, shrivel up to nothing. So all we’ve got to do is wait.

All this at least implies some link between the energy drain and the Doctor’s alarming condition. Fan theory time: what if the Doctor is deliberately giving up all his exotic time energy to destroy Mondas, in the same way the immortal Captain Jack over-fed the life-draining Abbadon to destroy it in Torchwood: End of Days? As Episode 1 made clear, these events are part of the established timeline from the Doctor’s perspective: maybe he’s realised this is the moment he finally needs to become part of history, rather than running from it. It’s definitely the kind of thing one of the new series incarnations might do…

The rest of the episode revolves around the previously unmentioned Z-Bomb. Quite how Ben suddenly knows that ‘we’ll all go up with it’ is unclear (presumably the Doctor told him at the same time as he explained how Mondas would be destroyed). The rest of the episode is a grim meditation on the use of nuclear weapons and the side-effects of the subsequent fall-out. The Cybermen only appear briefly, and are quickly eliminated by the weapons captured from their first landing party – which makes them seem much less of a threat.

Suddenly, the ‘ruthless’ and half-mad General Cutler is the real danger – hurling Ben off a gantry and then threatening to take the law into his own hands – and Polly, who criticised the Cybermen for being uncaring last week, is now advocating sacrificing Cutler’s son Terry for the sake of millions of human lives. It’s quite a pivot from the previous episode. I wonder how much of this was due to Gerry Davis, who gets a writing credit on this episode (and Episode 4), wanting to focus more on the human drama and less on the interesting but fairly static philosophical discussions that dominated Episode 2.

Next episode: The Tenth Planet – Episode 4