‘The Doctor wouldn’t do this. The old Doctor, the proper Doctor, he’d wake up. He’d save us.’ The Christmas Day special has been the last bow for the past three Doctors, but I prefer this. Sneaking in the new Doctor like a present under the Christmas Tree and giving us a chance to unwrap and enjoy, rather than just a tantalising glimpse. RTD leans into this, gleefully, with an episode that’s replete with all the festive trimmings, given an Avengers twist: (killer) trees, (deadly robot) Santas, a (cancelled) Queen’s Speech and a tangerine.

The result is a near-total triumph. But despite the success of Series One there was still the potential for this to fall flat. Could the 10th Doctor be a worthy successor to the ninth? In retrospect, with Tennant topping pretty much all the best Doctor polls since about 2006, it’s seems a foregone conclusion. The script – and the whole Series Two – is much more cautious. The new Doctor is kept largely offscreen for about two thirds of the episode (imagine if Troughton hadn’t really showed up until Episode Five of The Power of the Daleks), and even when he is onscreen he’s weaker even than Peter Davison in the first half of Castrovalva. Like Davison, he gets one brief moment of heroic lucidity before lapsing back into somnolence.

Unlike Davison, he’s terrible on the rebound, rallying magnificently for the showdown with the Sycorax. But until that point, Piper and Wilton largely have to carry the story. For both Rose and Harriet it reveals who they are without the Doctor to save them. Neither holds out much hope, although both step up to do their duty. But Harriet reverts to sanctioning the sort of massive weapons of destruction she fought against last time we saw her; Rose gives up on the Doctor (‘He’s left me mum’) and plans to sit out the invasion inside the TARDIS.

Which means when the Doctor finally comes round, he has to be magnificent to justify Rose’s complete change of heart. And luckily, RTD and Julie Gardner had cast Tennant, who entirely dominates the last third of the episode. In front of an audience of alien warriors and kidnapped humans, he brilliantly demolishes the Sycorax blood control scam, challenges their leader to a duel for the planet, wins, and for an encore brings down Harriet Jones’ government with six words. In twenty minutes, he has owned the role of the Doctor completely. It’s unfair to compare him to the classic Doctors, working in a very different production environment, and he’s hugely helped by a script that has total faith in him (unlike Castrovalva or The Twin Dilemma, which seemed much more equivocal about their lead characters), but that shouldn’t take away from the scale of this achievement. By 8pm on Christmas Day, David Tennant was The Doctor.

But what kind of Doctor? Fast talking, always moving, turning on a penny from cheeky humour to profound sadness, leaning in as if he’s talking to you in confidence, but with his eyes fixed on someone else because he wants them to hear. Fearless, impudent, ruthless. He swaggers across the screen. There’s so much here to unpick. His hypocrisy is almost breathtaking: ‘no second chances’ he declares as he dispatches the Sycorax Leader, before deposing Harriet Jones when she hears his dire warnings of Earth drawing attention to itself and emulates his ruthlessness. His casual rewriting of time, wiping the three-successive-term Prime Minister from the history books, clears the way for Mr Saxon and ultimately means the 10th Doctor’s end is in his beginning. And then there’s that hand – ‘That hand of yours still gives me the creeps,’ says Rose, not realising one day she’ll end up with the severed one. Plus, Torchwood make an appearance, setting up the Series Two mystery.

The details of this are all spot on: Big Ben being repaired after the Slitheen attack; the name check of Series One monsters; Harriet still having to flash her pass; Rose and Jackie watching the Mars Probe on the TV just like in Aliens of London. Using the TARDIS’ translation powers to indicate the Doctor’s incapacitation and recovery is genius, making a throwaway plot point a punch-the-air moment. Anyone who missed the Children in Need mini-episode gets the main beats replayed when the Doctor wakes up on the Sycorax ship, asks Rose how he looks, reminds Harriet of their first meeting, and declares, ‘I don’t know when to stop’. The effects are brilliant, too: the TARDIS crash landing, and the Sycorax ship appearing over London and shattering every window in the Gherkin. And we get our first glimpse of another part of the TARDIS as Murray Gold’s Song for Ten plays.

Back in 2005 I was a bit suspicious of Tennant (mainly because I stupidly didn’t like the way he said ‘Barcelona’ in The Parting of the Ways) and wondered whether he could match Eccleston. By the end of this I was sold. It’s a better first episode than Rose.

Coming Soon: New Earth