‘We need to get back to the future – 2017 needs us!’ Broadcast, surprisingly, during Match of the Day, this two-minute scene introduces Bill Potts, the first new companion since 2012, while throwing in Daleks, explosions and jokes about suckers.

‘Hello sweetie.’ The final River Song episode parks all the complicated timey-wimey flowchart stuff, the Inception elements of Last Christmas and even the Christmas Carol pastiche to tell perhaps Moffat’s simplest and most direct story. River Song’s nearly-full diary makes the point that, like Hell Bent, it’s about endings. Unlike Hell Bent, it doesn’t rage against them: ‘Times end, River, because they have to.’ There’s a sense of completion and closure, and, if not quite ‘happily ever after’, that the Doctor and River have found contentment together (with the final joke that their last night will last 24 years).

‘I can’t be the Doctor all the time.’ Another expectation-confounding Moffat finale. Once again, the series’ “arc” turns out to be a shaggy dog story: no-one died at Lake Silencio; the Impossible Girl wasn’t, and the Doctor never became the Valeyard at Trenzalore. In fact, the Hybrid – if it is the Doctor/Clara – does stand in the ruins of Gallifrey (assuming that’s where Ashildr is waiting), and threatens to unravel the Web of Time. And in the end, none of it really matters because the true arc of Series Nine was the discovery that, ‘This has to stop. One of us has to go.’

‘How long can I keep doing this, Clara? Burning the old me, to make a new one?’ A dry run for Twice Upon a Time, touching on many of the same themes – this Doctor’s weariness, wondering why it’s never someone else’s turn and he isn’t allowed to lose just once; dealing with the grief of losing Clara, of being the last one standing on the battlefield, and of having to take the long way round. It’s also a bit of a party piece for Capaldi, marrying Moffat’s love of an unconventional narrative with the chance to write what’s mostly a monologue (although in reality a lot of it is dialogue with a largely absent Clara).

‘So, this is your life, then? Just bouncing around time, saving people?’ The theme of Clara becoming reckless like she imagines the Doctor to be comes to an inevitable conclusion as she discovers despite everything she’s learned, she she’s not immortal – or at least, not yet anyway. Rigsy’s return, which prompts the tragedy that follows, draws a link between this and Flatline – the first story where Clara took on the Doctor’s role. Since then, she’s tried to convince the Cybermen and the Mire she’s got what it takes to be the last of the Time Lords. Instead, she’s left having to imitate the other man in her life, hoping that she can ‘die right’ like Danny Pink.

‘You must not watch this. I’m warning you. You can never unsee it.’ Mark Gatiss steers away from classic Doctor Who homage to do something more like an episode of Inside No. 9 – an impression unavoidably suggested by the presence of his fellow Gentleman Reece Shearsmith. It’s a pastiche of found footage horrors with a very No. 9 twist. And that’s about all there is to it.

‘Everybody does what they were always going to have to do from the very beginning. Sit down and talk!’ Cold Blood with Zygons. On the surface this looks and sounds profound, with the Doctor giving impassioned speeches about war and dead children, and the importance of forgiveness (I could really have done without the Hughie Green impression, but I can let that slide. I’m more dubious about whether it’s actually in the Doctor’s gift to forgive Bonnie rather than, say, the families of the aircraft crew she killed or the people her followers have slaughtered). It’s all very punch the air stuff, until you think about it for more than half a minute and realise that it entirely hinges on the Zygonists having no ideology and no aims, Bonnie realising what a silly girl she’s been and the Zygons all going back to their quiet, hidden lives.

‘You can’t have the United Kingdom. There’s already people living there. They’ll think you’re going to pinch their benefits.’ Peter Harness takes the Daily Mail’s nightmare scenario seriously, with a slow invasion of immigrants seeking to maintain their own culture, and then to supplant the indigenous population. The Zygons play into all the stereotypes, with their “community leaders” trying to contain the ‘radicalisation’ of the younger brood but unable to stem the tide, and the gloating Zygonists triumphantly declaring victory in the first battle.

‘I live in the world you leave behind.’ Catherine Tregenna, writer of some of the most striking episodes of Torchwood, arrives in the parent show with a script that similarly prioritises character relationships over action. The 21^st Century series has often raised the idea of the Doctor’s long life, and how living like a human being, day after day, is ‘the one adventure I can never have.’ This episode engages directly with it, of Ashildr’s life on the slow path, eight centuries of loss and heartbreak waiting for the man who did this to her to pop back in. She is another in a long line of girls (and boys) who waited, but of all of them she’s had to wait the longest and suffer the most.