The signature of Russell T Davies’ tenure as Dr Who ‘showrunner’ has been a sustained examination of the dynamics and the dramatic possibilities of the Doctor/Companion relationship – from the obvious (what if they DO IT), to the relatively unexplored (what happens to those left behind? what happens after you get left behind?). His vision of the Doctor, ultimately, is as an agent of change – which chimes with how the character’s been portrayed since Baker T, at least, but that tended to be situational change: the Doc as the random element that twists outcomes  differently. Davies’ Doctors (Tennant in particular) effect change on a personal level. One single adventure with the Doctor is enough to transform Donna’s outlook on life: two seasons turn a Peckham shopgirl into a gun-toting dimensional warrior. Spoilers follow if you haven’t seen the last episode: As Davros points out to him, he either kills you or makes you stronger (sometimes both, as with Kylie). His power as a mutational catalyst underpins the season’s sad ending – Donna has simply absorbed too much Doctorstuff, too fast, and one iota more would kill her.

So the hugely indulgent set-up for this season finale – salad of all the companions! – works on levels beyond new-fan service. It works on those levels too, of course, but it’s a final flourish for Davies’ study of what sidekickdom involves, and one Doctor Who with its rotating leads is uniquely placed to deliver. What other show could possibly get so much logical dramatic mileage out of a big cast reunion? If anything I’d have liked to see the Doctor out of action for longer and the assorted companions sorting things out themselves a little more, rather than relying on the man in the big blue box. The “six pilots” payoff scene was the most indulgent, and deserved, bit of all – a little flash of joy before the status quo, or lack of it, resets. It’s not just Donna: every companion is “just a temp” – here was a scene playing with the idea that it shouldn’t be that way. Has there ever been a notionally SF series quite so happy to embrace the sentimental? With RTD moving on, will there ever be again?

This is another level on which the themes of companionship and temping and loss and return resonate, of course: Doctor Who is a TV show for kids, brought back by adults who’d been changed by it, watched by more adults who’d never been quite able to shake it, and now passing it on to kids themselves. The clip-montages of scenes from the last four years were a showy goodbye from Davies; the final scene of the Doctor in the TARDIS, morose and alone, worked just as well. He’s had his faults as Who helmsman – there’ve been plenty of times where I’d have liked to decide for myself that the plot or details weren’t important to an episode, rather than have him rub it in – but “Journey’s End” proved to my satisfaction that he’s always had a grip on the show’s thematic and emotional rudder.