‘But if you could choose, Doctor, if you decide who lives and who dies, that would make you a monster.’ The centrepiece of Doctor Who’s imperial phase, as David Tennant and Kylie Minogue take over Christmas with a special episode so big it spills out of the traditional hour-long slot to pack in a pastiche of The Poseidon Adventure with a side dish of Die Hard. There’s a certain absurdity to it, but it only very occasionally tips over into outright shclock, such as Elizabeth II waving at a flying replica of the Titanic and wishing the Doctor a happy Christmas.

RTD sets the scene straight away, with a plush-looking Titanic ballroom, Kylie as a waitress, the Titanic revealed to be a spaceship and ‘Welcome to Christmas’ before a bombastic new arrangement of the theme music kicks in and the post-prandial audience settles back for the ride. The cast is quickly sketched in: the grasping businessman, the lovable competition winners, the professorial tour guide, a whimsical small alien, a dogged young midshipman and the tired old captain. As appropriate for a disaster movie, most have guilty secrets that as will leak out as chaos unfolds. The actors all get their characters and play up to the script (Chazen and Rowe sweet, working class; O’Brien sleazy and ruthless like the character he played in Corrie; Tovey guileless and steadfast). When Geoffrey Palmer’s Captain describes Titanic as ‘an old ship full of aches and pains’ we feel his own weariness; there’s a realism to his sadness that’s perhaps too heartfelt – it’s definitely the only moment I get past the brassiness of the premise.

Elsewhere RTD’s script picks all the key moments of disaster movies – blithely sailing into disaster despite all the ominous portents, like the malfunctioning Host robots (their design looks like Axons crossed with Voc Robots – which is made explicit when one of them gets its hand pulled off), the set-piece peril chamber (in this case, a narrow bridge across a fire chasm), and the race against time to escape death. Marvellously, the budget is mostly up to it, raising the bar again for what the show can now do (the exception, for me, is the final showdown between Astrid and Max, which is mostly done through close ups as if there’s not quite the money for more than Astrid’s operatic death fall). But the CGI is now even able to handle details like the bodies floating in space after Titanic’s hull is breached.

So, it looks great, and it ticks the right boxes for a big, Christmas Day event. Kylie is the perfect guest star for something like this: a big name to draw in viewers. Really, she’s not asked to do anything particularly stretching beyond being cute, and the Doctor’s rapid infatuation with her, coming off the back of his break-up with Martha, would be jarringly shallow if this weren’t a Christmas episode in the heart of cuffing season. More than the previous two specials (but increasingly the case for future years’), your tolerance for it is likely to depend on how much slack you’re willing to give an episode made for a specific event and a slightly different audience than usual.

The bits I don’t like: the Buckingham Palace sequences, which – understandably, but teeth-grindingly – veer into silly kid movie territory. The written-for-the-trailers, ‘I’m the Doctor. I’m a Time Lord. I’m from the planet Gallifrey in the constellation of Kasterborous’ speech. The rapid elimination of three survivors in quick succession. Astrid turning into animated blue fairy dust that twinkles across the night sky at the end. The thing is, all of these bits make absolute sense in the context of Doctor Who being the big TV event of Christmas Day, 2007, something that can only ever be true once.

And there are so many bits I do like: the Doctor’s desperate drive not to lose more good people (‘No more’ is a phrase we’ll hear again), which begins a theme that continues through to The Waters of Mars; the call-back to Last of the Time Lords’ ‘I can’t decide whether you should live or die’ with Mr Copper unconsciously forcing the Doctor to compare himself to the Master; Wilfred Mott – this Doctor’s nemesis appearing at the moment his hubris begins to show. This doesn’t trouble my list of favourite episodes. It’s not even on my list of favourite Christmas episodes. But it is, perhaps, the most iconic.

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