It's to the credit of the production team that "Partners in Crime" appeared fresh and exciting - because in truth, it was just money for old rope. Albeit very entertaining rope. A new companion is living out her life on contemporary Earth, little knowing that the Doctor is working undercover to defeat an extra-terrestrial threat from a former-Coronation Street regular. It's all a bit "Smith and Jones" isn't it?

But this is par for the course these days - we know how things work. We know that the emotional drama is being preserved for the thoughtful mid-season two parter, the big CGI spectacle for the two-part closing story and the historical caper for Weeks 2-4. Whether or not you begin to wonder when Doctor Who seasons needed to run to such a strict formula is another matter, but it probably makes sense that the fluffy Rusty space opera/comedy lite opened the season again; craftily, those in charge know that the very fact that Doctor is back after a break will generate enough publicity by itself - you don't need to waste an old monster or many "money" shots on an episode that'll be warmly received without them.

Even as openers go, "Partners in Crime" was good, up with there with "Smith and Jones" and easily better than the shakily-plotted "New Earth" two years ago. As someone who's never actually seen Catherine Tate in her own show, bar a few clips, it wasn't so much that I had an open mind about her casting as that I simply didn't see any reason to take to the picket lines yet. It speaks volumes that fans were overly cautious about Tate becoming a companion simply for something ELSE that she had done. One thing Russell T is good at is giving people a chance to step outside their box and shine, and shine she did. After just one episode, Donna is shaping up to be even better than the engaging but unwelcomely hung-up and earnest Martha; and it's about time we had a level-headed woman aboard the TARDIS, instead of a neurotic girl. Wistful, eager but still with a soft spot for her old Gramps, Donna is a regular of the like not seen in the show since Barbara - once again, a companion we can like, not pity. This was of course a totally unrealistic turn-around from the shouty bossy-boots that nagged the Doctor while he defeated the Racnoss, but quite right too. You didn't think they were going to keep her unlikeable did you? Have faith...

Elsewhere like "New Earth" and "Smith and Jones", there were height-defying chase sequences, a slightly gruesome monster attacks sequence and a cute don't-think-about-it-too hard whizzy fix by the Doctor to sort things out. Oh and one genius-like, superbly directed "how on Earth can they doooooo that!" moment too. It's a shame we didn't see more of the Adipose, but the disadvantage of being a savvy fan rather than a kid is that you are counting the money shots as they appear. Fair enough, we were never going to get scenes of them rampaging through Cardiff infiltrating homes with that big expensive volcano due next week - but it was a welcome change in itself that for once the alien menace DIDN'T want to invade the Earth. Sinister global companies led by suited businesswomen are also becoming an occasional series staple: this was all a little bit "Invasion of the Bane" as well.

But "Partners" was far more than a copycat episode, despite the lines stretching back to a clutch of previous New Series episodes. After all, no-one complains seriously about the number of Earth invasions of nuclear power stations in the Pertwee years, or about the volume of moonbases visited by Patrick Troughton. To an extent, this is where the current business of the series is at, and we know that Episode 1 of Series 4 is little more than a kicking off point. It won't be up there at the top of the stack come the seasons end, but did you want the best out the way first? It's sole purpose was to scream "Doctor Who is back - let the fun begin"!

Si.