Much of "The Christmas Invasion" is the same as what had gone before. The script is almost Russell T. Davies by numbers, with a red herring and copious soap outtakes on Rose's estate and News 24 coverage (cf. "Aliens of London") filling up much of the opening segment. We also have the return of Harriet Jones, also from "Aliens of London", and we're asked to believe that this stupid woman runs the country now. Obviously, she has a comedy catchphrase, with "Harriet Jones, MP for Flydale North" becoming "Harriet Jones, Prime Minister". Somehow the counter-catch phrase, assorted characters stating that they know this, makes it even worse - she's just made to look even stupider, and Penelope Wilton is utterly unable to get past the shocking material she's dealt. There's poor comedy throughout, sadly.

The plot is fractured into three rough segments - The Doctor and Rose arriving back in London and the former's malaise; the 'pilot fish' section; and the climactic battle with the alien Sycorax. The 'pilot fish' feel very much like padding. The early visuals as they try to kill Rose and Mickey in Santa suits are impressive, and give the red herring (no pun intended) that we might see the Autons. Even once this is clearly not the case, they still have potential, and the script totally fumbles the issue.

What exactly are they, aside from an idea pinched from a National Geographic documentary RTD caught the night before writing this? Why, and to where, do they teleport? Why are they chasing Rose and The Doctor for the TARDIS energy when the Sycorax are doing nothing of the sort, instead seeming to invade Earth for simple conquest? How do they manage to turn up very shortly after the TARDIS gets back to Earth, yet manage to get Santa costumes and firing brass instruments and stake out Rose's preferred shopping centre? Where exactly do they go? Where do they get the Christmas tree - do they have a stockpile of the things just in case they arrive at a planet that celebrates Christmas and they need to kill the residents of a flat in a topical way? Why not just go up and kill everyone? What, actually, are they? Not for the first time since the series' return, they're a loose metaphor stretched beyond breaking point, a tiny amoeba of an idea forced to carry 15 minutes of an episode.

Once this nonsense gets out of the way, the Sycorax turn up, and they're rather good. Aside from a sizeable make-up budget, there's little to distinguish them from any number of invading meanies, but they are well-done, and the blood control is a nice idea. Soon after this, The Doctor properly wakes up, and the thing totally changes gear.

It says something for Tennant that he lifts the whole episode single-handedly. Looking back after his first full season, he's possibly never quite beaten this little gem of a performance. Maybe it's that the contrast to the miscast Eccleston, but this electrifying, swashbuckling performance was the first thing from the revival that made me jump for joy. He has an instant presence, and makes The Doctor utterly magnetic for the first time in far too long, and manages to pull off some very dodgy dialogue with considerable panache. It's a big relief after the overdone glimpses in "Bad Wolf" and the Children in Need Special.

The only bit he can't quite pull off is the banal sequence in which The Doctor destabilises Harriet. While the concept is sound, and a welcome echo of The Doctor's political dabbling in "The Happiness Patrol", here it's wholly implausible. Even just not letting us know what The Doctor said would have been hard to swallow, but the results achieved by "Doesn't she look tired?" insult the viewer's intelligent. Thankfully, there's a surprisingly sweet wrap-up scene at the Tyler's place.

I really can't stress enough how integral David Tennant is to the success of this story. With practically any other performance, this would have been absolutely terrible. However, the vibrancy he brings masks some of the shoddy scripting, and means the episode finishes with an air of tremendous promise.

Review written: 14/07/2006
Series 2 Vol. 1 ("The Christmas Invasion" & "New Earth") @ Amazon.co.uk