AS that good friend of the Doctor, the Brigadier, once said when faced with the Time Lord's regeneration: "Here we go again".

Except this time, after four painful years of Matt Smith, the BBC appears to have got it right with Peter Capaldi.

It is the choice of age before youth, tall before short and Scottish before English (which has worked several times before).

The previous Scottish Doctors were Sylvester McCoy and David Tennant, but what Capaldi has over both of them is age.

He is 55, older than any of the other actors to play the role other than William Hartnell, who was also 55 when he was cast as the first Doctor in 1963.

That means the casting of Capaldi is a kind of return - the show that travels in time has looped back to the best place to find inspiration: the beginning.

As Stephen Hawking, who is right about most things, put it: "William Hartnell was older and that gave him an air of authority other Doctors lacked." Capaldi has the same potential.

But as well as age and the dignified air of a few grey hairs, there's something else that's promising about Capaldi - something we saw in The Thick of It and will hopefully see in Doctor Who. It's a madness, an anger, the feeling of an alien among humans.

It's a quality the greatest Doctor, Tom Baker, certainly had and I wonder if Stephen Moffat, who runs the show, is trying to summon those glory days again. It would be no bad thing.

Finally, Capaldi has also one other quality in his favour. When he was 15-years-old, and living in Glasgow, he wrote to the Radio Times and described his love of Doctor Who. All the best actors who have played the Doctor had that love, all the best of them saw it as more than a job. The choice may not have been a surprise (bookies can time-travel, it seems) but it is promising.