DOCTOR WHO: They were once pals, but now Time Lords Doctor Who and The Master are at each other's throats.

Miss Marple, James Bond, Dr Who - if you get the chance to play one of these characters, then you must have to face up to the fact that with that large part of the population who possess the loyal gene, you just can't win.

Personally, I still stand by Sean Connery and his Mt Rushmore dimples as Bond, and I'm possibly the only person in the world who feels a tender nostalgia when I recall Margaret Rutherford's defiantly wide-of-the- mark Miss Marple seeing something rotten through the train window as she is making her way to St Mary Mead on the 4.51 from Paddington.

Dr Who (Sunday, 7.30pm, Prime), of course, gets over the loyalty issue by making the title character able to regenerate when near death. (It's very useful being a Time Lord. You should ask for it next time.)

The new Doctor has the same memories but another body. For the viewer, this is particularly useful given the fact that as you casually channel graze in the desperate hope of finding something worth watching, you can see any number of Dr Whos crossing your screen within seconds of each other.

This logical persona switch doesn't stop the viewer from forming attachments, however.

Over the years, as I drift in and out of watching this programme, I've either bonded or not.

I never much liked Jon Pertwee (1970-1974). He was too Restoration foppish. How many scientists look like that?

Peter Davison (1981-1984), looking as if he is about to open at bat for some minor county, is forever a country vet or a country GP or a husband lacking in moral fibre. Even calling him Doctor made no difference: by dressing him in the way they did - as a country vet, a GP, etc - they just made him even harder to believe in.

In 1996, we got Paul McCann (Oscar Wilde with testosterone injections), followed briefly in 2005 by a pleasantly unremarkable Christopher Eccleston.

Ah, 2005. That regenerated into a good year for Doctor Whos. David Tennant enhances any screen that frames him, but he was a particularly good choice for this character.

For a start, he has a wired energy and a terrifyingly intelligent face. If he started to explain, say, black holes, to you, you would shut up and listen and, what's more, after the explanation, you might well even have a vague idea about what he was on about.

This year, we have got our 11th Doctor and the fuss around the choice of actor to play him equalled the interest in who's going to get the ball out of the scrum in the Rugby World Cup, or who's bedding some A-list celebrity. Down at the bookies they were even taking bets on it. Matt Smith was a rank outsider.

So how is he filling David Tennant's huge boots? Very well. If anything, he is even further along the Asperger's continuum than Tennant. They resisted the urge to cast someone as physically different as Joseph Paterson and have chosen Smith, who looks far more like the last Doctor than is usual in this series. He has the same intelligent leanness, and the same ability to distance himself from the emotional. All Doctors at some stage have to tear themselves out of the arms of an adoring sidekick before disappearing in a Time- Lordish way.

Smith is going to be good at this. You can tell by the way he doesn't get overwhelmed in the current series by the ground taking on a life of its own, in a Kaitangata Twitch sort of way, and dragging hapless people through it. It's not the death of an innocent bystander. It's a problem to be solved.

With drama of any sort being thin on the ground on our screens, it seems that Doctor Who remains an appealing enough watch. It does seem to know which bits of tradition to stick with and what to let go.

There has never been a Doctor who hasn't surrounded himself with characters to ask the questions that the audience needs answered, whether it be something terrifyingly scientific, or just gut-wrenchingly poignant, such as last night's "Can you get my Dad back?"

As with many other British television dramas you watch in the comfortable knowledge that you're going to be taken to hell but will definitely be coming back. It's excellent at creating a scene of placid, often bucolic beauty. Last night's episode opened with 2020 - the year, not the vision - but we may as well have been looking at rural Britain 100 years ago, so pleasant were the rolling hills, so solid the stone farm buildings and so permanent the graveyard.

The special-effects department also do fine baddies, or rather rivals. Last night, the people pulling the apes (us - that's how we seem to the sophisticates from the future) through into the ground owed quite a bit to spiderman.

"You're beautiful," says an admiring Doctor to his prisoner from the future. Well, yes. That's because even though she had skin like a well-dressed tuatara, she also had eyes just the right shape and distance apart to nicely fit with a 21st-century idea of beauty.

And although there's not much good to come out of BP's oil disaster, the scriptwriters of this latest story must be thinking "Yes!"

It is all based around a drill too far, a drill too deep. Sometimes science fiction should be listened to.