One of the delights of the Doctor Who revival has been, for me, the episode School Reunion, that popped up in David Tennant’s maiden season. This was the one that brought back Elisabeth Sladen’s Sarah-Jane Smith, and effectively triggered the related spin-off series too.

But it also continued a trend to add depth to the 'side' characters in Doctor Who, that the show didn’t always manage to do. Originally there as much as a narrative device (or in the case of Bonnie Langford’s Mel, to scream to a point where you reached for the remote control), to help explain what was going on to the audience, the assistant gradually started to squeeze out some back story for themselves, too. It’s no coincidence that this piece goes up on the same day as an interview with Sophie Aldred, whose character Ace had perhaps the first significant signs of a fully rounded backstory.

And we’re not talking about Billie Piper’s entourage here, although that had its merits (that should earn a few rants in the Comments field alone...). We’re talking about particularly the likes of The Curse of Fenric, where Ace meets her mother, and holds her infant self in her own arms. It’s a terrific story, and proved that Who could work without the title character slap bang in the middle of it.

School Reunion took the next logical step, though, and picked up what happened when the Doctor has gone off on his travels, and left his assistant behind. And while there was some fear at first that the return of Sarah-Jane Smith and K9 had a bit of a gimmicky feel to it, by the end of the episode School Reunion, you had to admit they’d come up with something very, very special. Arguably they couldn’t have picked a better, or more iconic, assistant to do it all with.

How great it was to see Elisabeth Sladen presenting the Doctor with consequences of his actions that weren’t all about death and destruction. To get across to him, without resorting to mawkish sentiment, that there are repercussions to him leaving all these assistants across the galaxy once they’ve finished travelling with him.

The key, of course, was the quality of the writing, with this one of our favourite episodes since the revival of the show. The lovely thing was that it added depth to a character that had been long since written out of the show, and as a result, gave added scope to those who had followed.

Whether we’d want to see too many more assistants revived is a debate for another time, because most of them served their time and rightly moved on. That’s not to say we didn’t enjoy them, but many of them were of their time, and don’t need to be revisited.

But perhaps the main reason? School Reunion said much of what needed to be said, and for a long time will stand as a highlight of Doctor Who. As we wrote originally when we talked about it, it’s enough to make a grown geek weep…