So “The Christmas Invasion” then. Perhaps the only episode of Doctor Who in the last 20 or so years not designed to stand up to the rigours of the home video (let alone DVD recorder with hard drive) age – and that’s possibly as it should be. Watched on Christmas Day itself, the episode was an absolute cracker, utterly refreshing and just the tonic to head off the impending state of vegetation that usually descends upon the nation at around teatime. “The Christmas Invasion” was full of pace and wit and, most importantly, spectacle. This was truly the first ever Doctor Who episode that wouldn’t have looked out of place on the big screen, and for Christmas day that was enough.

Yet no episode of Doctor Who is ever just for Christmas. Even if you set aside the loyal fan base for one moment, these days television dramas have to be able to live on in the short to medium term memory of the viewer in order to entice them back for more. Besides, with the likes of BBC3 and UKTV Gold around, the average television viewer will probably happen across “The Christmas Invasion” again in a few weeks time, and if on second viewing the episode appears to unravel in front of their eyes into a string of inconsequential scenes and a threadbare plot (with a frankly ropey dénouement) then the chances of them tuning into series two (which, by the way, from the trailers looks brilliant) becomes ever more remote.

In terms of where we are with this new run of Doctor Who, “The Christmas Invasion” was always going to be a difficult slot to fill. Although there is a new Doctor to play with (and we’ll get to him in a bit), none of the elements that the production team introduced in series one are new anymore. So whereas the introduction of Rose’s estate was an innovative move that offered a distinctly original perspective on the character of the Doctor, with “The Christmas Invasion” it has become simply part of the (now) established Doctor Who formula. Whether or not the production team will be able to come up with further ways to make us view the concept “as new” remains to be seen, but undoubtedly this fundamental element behind the success of Doctor Who in 2005 is getting exhausted quickly, and one must pause to wonder what will be left once time travel and aliens become passé once more.

For those looking for further indications of the immediate future of Doctor Who, “The Christmas Invasion” offers portents of both doom and cheer. The bad news is that Russell T Davies still seems to believe authentic and entertaining dialogue is enough to paper-over weak plotting. Indeed in this respect, “The Christmas Invasion” employs the art of the baked bean ending on a scale far grander than seen in series one. This is dispiriting news for those who hoped the series’ lead writer would have taken time to assess the relative strengths and weaknesses of his contributions to date. However, on the evidence of this episode we can expect further adventures with inconsistent pacing (those scenes in UNIT HQ seemed to take an absolute age), unconvincing back stories (the whole UNIT set up somehow feels wafer thing) and plot resolutions reliant on pressing conveniently placed buttons at the right time. On the other hand, David Tennant is absolutely superb, demonstrating a remarkable ability to deliver dialogue in a constantly engaging and surprising manner. Indeed, perhaps the best testament to Doctor number 10 is that within minutes he made Eccleston’s performance seem actorly, mannered and very un-Whoish. Certainly the most rewatchable scenes in “The Christmas Invasion” are those featuring Tennant at their centre. His multi-layered and clever delivery is able to withstand constant reviewing, and he is surely the series’ most powerful weapon as it embarks on its second run.

However for all the gripes about Davies’ rather weak script, the concluding motif (that of the decaying space ship bringing about an artificial Christmas scene) was poetically realised and provided at least a satisfying thematic conclusion. As too did Harriet Jones unexpectedly adhering to the grand old Doctor Who cliché of the military/political appetite for destruction. Tennant’s rebuke conjured up the very spirit of Jon Pertwee berating the Brigadier and was all the better for it. Whilst it all might not have been quite as Christmassy as we had been lead to believe (with killer Santas and buzzsaw Christmas trees merely an appetizer to the main, non Yuletide focused action), it did at least look and feel totally different to every other programme broadcast that day. With the “me too” copycats in the shape of Torchwood and Eleventh Hour on their way in 2006, distinguishing Doctor Who from the pack is going to become increasingly important, and so for that reason at least “The Christmas Invasion” has to be cautiously commended.