Every major sci-fi franchise needs an origins story and you might like to think of An Adventure in Space and Time as a something of the kind.
The difference is that the events of this feature-length making-of drama about the beginnings of Doctor Who took place not in the show's fictional universe, but in the real world. Well, mostly they did.
It was in part a Sixties-set workplace drama, like Mad Men or The Hour, in which an ambitious young woman banged her perfectly coiffed beehive against the era's glass ceiling.
That woman was the producer Verity Lambert and for casual Doctor Who fans such as myself (Favourite Doctor: David Tennant), the show's progressive employment record was a revelation: Lambert was at that time the only female producer at the BBC and director Waris Hussein was the first Indian-born director. What a shame their legacy is yet to be fulfilled with a female or non-white Doctor.
In the end, however, the story belonged not to Lambert (Jessica Raine) or Hussein (Sacha Dhawan), nor even to the larger-than-life, back-slapping head of drama Sydney Newman (played with obvious zest by Brian Cox), but to the actor William Hartnell.
David Bradley played the first ever Doctor as a cantankerous codger, old-for-his age at 55 and so bored of playing sergeant majors, that he filled his hours drinking whisky and growling at his granddaughter instead.
Hartnell was initially reluctant to make a move to children's TV – he was a film actor, after all – but over the course of his three-year stint we saw how he began to delight in this new fan-base. He signed autographs for thrilled schoolchildren in the park and even led them in a quick game of Daleks'n'Doctors.
In Doctor Who, an end is always a beginning, and so it was with Mark Gatiss's cleverly resonant script. Not only did we have the always exciting opportunity to see two Doctors share a screen, but Hartnell's pathos-tinged handover to Patrick Troughton (a cameo from Gatiss' League of Gentleman chum, Reece Shearsmith) was also followed by the apparition of a rather more recent incarnation.