PLEASE NOTE: IF YOU'VE NOT SEEN THE EPISODE, THIS IS A SPOILER-FILLED REVIEW

I’ve said it before and I’ll say it again: Doctor Who will miss Russell T Davies.

The Waters Of Mars very much saw the show turning down a much darker path, and for long parts is perhaps best described as one of the Doctor-less episodes, yet with the Doctor slap bang in the middle of it.

Russell T Davies has probed at this before, at how the Doctor leaves behind a line of casualties in his wake, and how his very arrival at the scene of something means calamity is never far away. But here his script – co-written with Phil Ford - attacks the central character of the Doctor in perhaps the most potent way: he renders him utterly, utterly helpless.

Sure, he’s uttering words, and sure, he’s running around corridors. But ultimately, there’s a genuine feeling pumping through much of Waters Of Mars that for the first time in a long time, there’s nothing that the Doctor can do.

But all of this shouldn’t come as a surprise. Davies’ best episodes – with the exception of the superb Midnight - have invariably come when he’s writing on the home strait to a big finale. The Stolen Earth, Utopia and Bad Wolf were all strong to varying degrees, and while the pay off has never convincingly matched the build up (with, perhaps, the exception of The Parting Of The Ways), Davies damn sure knows how to tantalise and build-up an audience.

With The Waters Of Mars, he does it again, although that’s not how initially it seems things are going to pan out. Particularly in the early part of the episode, it seemed a jamboree of classic horror and monster movies rather than anything particularly dark. It can’t just be me who had visions of The Thing in their head when it was revealed that everyone could already be infected by the water that was causing the creation of some not particularly friendly monsters.

The use of water, to be fair, was an inspired plot device, even if it did ultimately seem a bit of a distraction from the main work of the episode. When Doctor Who taps into simple, everyday things it’s usually at its most unnerving, and when the Doctor warned here that water is patient, it managed it again. Ironically, of course, it was the single drop that was the most dramatically effective, rather than the hosepipe dribble coming out of the monsters’ mouths.

The characters themselves, most of whom proved to be water-cannon fodder, at first came across as the usual demographically-diverse collection of faces. The first human off-world colonists in history, we meet them working on Bowie Base One (see what they did there?), clearly isolated and clearly unlikely to make it to the end of the episode. Step forward the superb Lindsay Duncan though, who is just brilliant as Adelaide Brookes, the leader of the team on Mars.

Whenever the focus switches away from the ensemble and more onto her, The Waters Of Mars immediately feels the benefit. Her speech to Tennant at the end, about how he’s wrong, is brilliantly delivered. It’s in line with the best moments of the episode, and the script wisely slows things down an awful lot for long periods of time to let moments like that resonate.

Take too the part where Tennant is telling her about her fate, and the understated reaction on Duncan’s face. When he drops out the word “consolation” to her, it has real resonance and impact.

Duncan’s performance is matched though by Tennant’s, in arguably his best ever performance in the show. For those who’ve complained about the wild-eyed, hyperactive Tennant of earlier episodes, this is the perfect riposte.

The scene near the end when he’s walking away, hearing the radio chatter of the doomed inhabitants of Bowie Base One, demonstrates simply superb acting. For large chunks of this episode, the Doctor is a very still and haunted man (spitting out lines you never thought you’d ever hear the Doctor say), and Tennant for me absolutely nailed it. Take too the moment where he’s trying to convince himself that he’s effectively the boss of time, and his decision to go against its laws by affecting a fixed point: he utterly owns the role, and it’s really going to miss him.

Memo to Matt Smith: you’ve got one hell of a job on your hands.

Furthermore, this was a Doctor Who episode with consequences. Adelaide’s presence on Mars was a direct result of the events of The Stolen Earth, where a Dalek stared her straight in the eye and then left her alone (we’ll come back to that in a minute). The Ice Warriors may have contributed to the events on Mars in the first place. And then there’s the consequences to come, with the summons from the Ood at the end, with Tennant’s Doctor realising – even if he’s running from it – that his time is nearly up.

It’s so well done here that you can’t help but scan the Radio Times to see if, by some miracle, the next episode is on tomorrow. There’s no immediacy to the cliffhanger, rather a festering feeling of impending doom. It works all the better for it, too.

Picky time, though. There was still room for a little comedy in an otherwise very dark story, the best of which was Tennant’s aside about he hates robot animals, albeit with the exception of dogs. But less successful was Gadget, who looked like an in-bred version of Johnny Five from Short Circuit, particularly when filmed from the side.

I also wasn’t hugely keen on the monster side of things this time, although my feeling is that’s more down to the fact that the emotional battering the Doctor was taking was by far the most involving part of the show. The creatures were perfectly serviceable, but – as with Planet Of The Dead – they were more the sideshow here than the main thrust of the episode.

Also, I can’t help thinking there’s a logic gap in there somewhere. If the destruction of the Mars base is a fixed point in time, and if Adelaide’s presence there was a result of the events of The Stolen Earth, then how could the Dalek we see have known that?

That might be me misreading things, but the Daleks would have needed the events of The Stolen Earth to play out and for decades to pass before knowing how vital Adelaide was to time. Surely, therefore, the Dalek there and then should have just shot her, as it wouldn’t have known of her importance? There’s no doubt some clever time-travelling answer to that, but it did jar a little for me.

Those slight grumbles aside, though, I thought The Waters Of Mars was terrific. We saw in Torchwood: Children Of Earth that Russell T Davies can write stone cold hard drama to a very high standard, and this is surely as far as he’s yet pushed Doctor Who in that direction.

The Doctor, as presented here, is a lonely man, without a human companion to act as a counter balance, and he starts going off the rails fairly swiftly as a result. That’s not the Doctor that we’ve seen on the side of lunchboxes and on school rucksacks for the last few years, and the really intriguing thing is that, surely, further darkness lies ahead.

On the basis of The Waters Of Mars, Christmas – and The End Of Time – simply can’t come quickly enough. For it can’t just be us whose geekbumps soared off the scale when the trailer for the final specials kicked in at the end.

The Doctor vs the Master with some assistance one way or the other from The Ood? We know what we’ll be doing on Christmas Day…

See also:

• Russell T Davies & David Tennant on The Waters Of Mars
• First picture from Doctor Who: The End Of Time

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