AS Christmas approaches, Mark Gatiss will be out among the shoppers in his home town of Darlington but I doubt you'll recognise him as he hasn't been himself over the past 12 months.

The real Gatiss has been hidden behind a number of guises, including real life personalities Johnny Cradock, husband of chef Fanny, and University Challenge questioner Bamber Gascoigne. And next he'll be seen disguised as Rat in BBC1's new adaptation of children's classic, The Wind In The Willows.

When we spoke he'd just finished playing another real person, writer Robert Louis Stevenson, in yet another BBC1 film, Jekyll.

As the title suggests, this is a reworking of Dr Jekyll And Mr Hyde, but more than that he cannot say as the project is hush-hush, just like his role in the next series of Doctor Who.

Gatiss is not only busy but multi-skilled. Having made his name on stage, TV and cinema as one of the award-winning comedy troupe, The League Of Gentlemen, he's now carving a solo career as an actor, which is what he trained to be in the first place.

He'll be appearing without any disguise at a book signing at Waterstone's in Darlington tomorrow. The Devil In Amber is the second in his Lucifer Box books, following the successful The Vesuvius Club. Box is a daring secret agent - "the gorgeous butterfly of King Bertie's reign, portraitist, dandy and terribly good secret agent" - who, in his second adventure, finds himself up against a fascist leader and framed for murder in New York.

He's a man who rates himself highly, remarking: "I cut quite a dash. I'm afraid I rather fancy myself, but then everyone else did, so why should I be left out of the fun." And then again: "I'm always trying to recapture my youth - but he keeps on escaping."

Gatiss was commissioned to write three books, saying the second was easier to write. "I learnt a lot by doing the first and I had this idea for the next as soon as I'd finished it. Instead of doing another Edwardian story, I'd do a book 20 years on. That really inspired me, to take the same character and put in a different age of detection," he explains.

His research included reading a lot of Bulldog Drummond stories - "a guilty pleasure" - and he's pleased with the result, The Devil In Amber. "Like The 39 Steps, it's one long chase and is much more of a thriller than the first book," he adds.

He already has a title for the third, Clawhammer, and "bits and pieces" of ideas. The influences are less obvious than before, although he points to "early Ian Fleming" as an indication of the style.

The Vesuvius Club earned him a best newcomer nomination at the British Book Awards, part of the favourable reaction that he admits took him aback. The book is now in its ninth printing, and has been published in the US, Italy, Germany and Russia. "It has sold very well and, after doing publicity for the second one, I realised that lots of people really enjoyed it," he says.

A film or TV version seems an obvious next move but, so far, plans haven't materialised because "people just want to make it like something else and I don't see the point. I'm in a very lucky position, I don't have to do it. I'd much rather not do it at all than do it badly".

He's keen that any screen version should capture the cheekiness, the sense of fun of the original and points to The League Of Extraordinary Gentlemen (no relation to his League) which was a great comic book but a very ordinary film.

What he is pleased about is playing Rat in the BBC1 live action version of The Wind In The Willows. Little Britain star Matt Lucas is Toad in the adaptation by Newcastle-born Billy Elliot writer Lee Hall.

"Rattie is just one of those parts I wanted to do. I auditioned for it and completely threw myself into it. It can completely backfire because if you want a job very much it can be the worst audition you give. I went for all the animal stuff they asked me to do which, in the end, we didn't do. And I watched Ring Of Bright Water," he says.

"The experience of filming in Romania was quite challenging but we had a great time. We were at the castle Bond was at in Casino Royale. It was quite hot and a lot of the story is in winter so we were in three pairs of tweeds.

'I had the idea of having a David Niven-ish moustache which terminated in whiskers. The make-up suggests animals. I had false ears, moustache, teeth and a wig made of yak hair which is very tough."

That's showing on New Year's Day, the day after Gatiss can be seen in Fear Of Fanny on BBC2. The play about one of TV's first celebrity chefs, Fanny Cradock and her monocled husband Johnny, was premiered on BBC4 earlier this year.

He welcomed the chance to work again with Julia Davis - they were in the comedy series Nighty Night together - and to show Johnny's role in the relationship. "It's quite a background part but I tried to bring some pathos to it. The script was beautifully written. It stresses that although they threw everyone else away, they were totally devoted to each other. It's a curious love story. But that's the last of my broken, spineless husbands I'm going to play," he says.

He appeared as Bamber Gascoigne in the film, Starter For Ten, another in his real people roles. "You bear a responsibility when you're playing someone real, although it's different when it's someone long gone like Stevenson," he says. "Bamber was supposed to be visiting the set when I was doing him but he didn't appear."

The other big thing in his life is Doctor Who. He's a lifelong fan, who names Jon Pertwee as his favourite time lord. "I adored him as a child. I remember when he left I was utterly bereft, and it took a long time to warm to Tom Baker," he recalls.

He's written Doctor Who books in the past and wrote an episode when the series was first revived the other year. He was too busy to write one this year but achieved his dream of appearing in the show. "It came completely out of the blue. I play a mad scientist, that's all I can say. It's a really wonderful part and was definitely worth the wait," he says.

"I was pinching myself that it was true. The whole set-up is like any other job but it's not for me. It was all night shoots. The hours were very tough and it was quite gruelling, but obviously I was never going to complain.

"There were a couple of moments when the Doctor Who-ness hit me, like being shut in a machine filling up with dry ice. It was like watching myself in an episode."

We probably haven't seen the end of The League Of Gentlemen. He says they're on a sabbatical, soon to reconvene and talk about the future. "We're not going to do something just for the sake of it. We'll have to see what comes to us," he says.

"Personally, I've had a great year and done a lot of things. I was able to commit two months to do The Wind In The Willows, something I haven't been able to do before because of The League. I've done lots of acting and been very pleased with the response to what I've done. I'd like to do a lot more."

* Mark Gatiss will be signing copies of The Devil In Amber (Simon & Schuster, £15) at Waterstone's in Darlington tomorrow from 6.30-7.30pm

* The Wind In The Willows is on BBC1 at 6.20pm on New Year's Day.

* Fear Of Fanny is on BBC4 at 9pm on Christmas Eve and on BBC2 at 9pm on New Year's Eve.