Doctor Who and popular culture have never made for good bedfellows. During the series original run, its flirtations with youth-speak (“Gordon Bennet!”) and chart music (John Smith and the Common Men, indeed) were shamefully embarrassing. If you ever saw Ian Chesterton grooving to the Beatles, you pretty much had your perfect metaphor for the show’s relationship with the zeitgeist: painful, uncoordinated and hopelessly out of time.

For whatever reason, Doctor Who was always awful at acknowledging any cultural movement post-1950-something. Okay, so the companions may have flirted with the fashions of the day but never with anything approaching reality. In the early 1970s, go-ahead female journos were about as likely to leap out onto an alien planet dressed up as Andy Pandy as they were likely to – well – leap out onto an alien planet. This wasn’t necessarily a bad thing, of course. That the series seemed to take place in a Dan Dare universe of no profanity, sex or drugs (“The Talons of Weng-Chiang” not withstanding) was actually quite pleasing: a cosseted world of rolling fields, high teas and England at the centre of the globe (not Britain, mind – Scotland, for one, still remained a misty, exotic far flung locale).

And then there was tonight’s episode. Fusing an action sequence to Britney may not be eyebrow-raising stuff elsewhere – Hollyoaks does it all the time – yet here it was a glorious and wholly successful aside that proved not only is Doctor Who part of the here and now, but that he’s finally checked in his ration card for an iPod. Despite the fact he’s still associating with a plum-in-her-mouth actress who’s playing below her age and dropping her h’s because that’s how real life kids talk, none of this felt forced. Although a huge new back-story (and we’ll get to that in a minute) was dropped into proceedings without warning, this insistence of placing the programme in the same tableaux as today’s obsessions was probably the single greatest thing about the comeback so far – and the decision that will best secure its longevity.

It’s not that I’m saying the programme needs a guest appearance from McFly every week, it just has to continue returning to these touchstones of reality; these anchors. Rose farting about on her mobile phone, referring to the deliciously amoral Cassandra as “Michael Jackson” and making gags about the Doctor being a lousy date – they all allowed the viewer to whole-heartedly believe in what was happening, and thus opened up the imagination. This is a Doctor who really could land his TARDIS in your street and whisk you off for amazing adventures before stopping for chips on the way home.

Like every fan, before this episode started I was prejudging: full of aliens, reportedly camp humour and expansive sci-fi – okay. Buoyed along by last week’s instalment, I knew it was going to be good, but just not that good. Yep, I hate to admit it, but on the verge of the second edition I was “ranking the season” and had this one earmarked for the bottom of the heap. But actually it was fantastic. We had real jeopardy, top humour, exquisite characterisation (RTD having totally re-thought the whole business of being a Doctor Who companion) and that back-story.

If this is how the series has been influenced by – gulp! – Buffy, then I can live with that. The reported destruction of the Doctor’s home planet was beautifully played, and presented a truly multi-layered plot point that titillated us dedicated ones with its sheer audacity, but also rolled out a nice element of tragedy for those who didn’t know any better. More than that, it presented the Doctor with something utterly new and potentially dangerous: character development.

Yes, we already know Christopher Eccleston is leaving, but the fact of the matter is, the Doctor is changing right now. And against all the odds, it’s great.