For the past nine months Davies has been awoken at 8am every day by a courier bearing the rushes from the previous day's filming of Doctor Who. He may be credited with singlehandedly reviving family drama on British television but Davies prefers not to be on set when his script is being filmed. The new series started on BBC1 last night and next month Torchwood, BBC3's X-Files-style Doctor Who spin-off, which Davies also writes, goes into production in Cardiff.

As chief scriptwriter on Doctor Who, overseeing the work of fellow scribes of the calibre of The League of Gentlemen's Mark Gatiss and Coupling creator Stephen Moffat, Davies has, true to his word, removed the shackles from his imagination. A sinister race of catwomen, an encounter between Queen Victoria and a werewolf, the devil and a terrifying squid-like monster all feature in the second series.

Alongside action-packed adventure sequences, Davies also explores the Doctor (David Tennant) and his assistant Rose Tyler (Billie Piper) on a more intimate level.

"Stephen Moffat has written what is practically a love story for the Doctor in episode four.

That's never been seen. It's very understated, very beautifully done, but it's nonetheless a Time Lord falling in love and Rose's reaction to him falling in love with someone else."

Elements of the old Doctor Who, including the Cybermen and K9, make a comeback in series two, following the reappearance of the Daleks in the first series, when Christopher Eccleston brought a wry northern charm to the part of the Doctor.

Davies is a great believer in the backstory. He was particularly gratified to receive an email from a fellow Manchester resident, The Royle Family writer Craig Cash, whose enjoyment of the Dalek episode was greatly enhanced because his children were so excited that their parents knew more about the next week's monster than they did.

"When I was young, my dad used to teach classics and I used to love the Greek and Roman myths. If you read book one of Harry Potter, it's steeped in backstory. For something to come with mythology to it really helps to give it a resonance. A young audience likes an echo of the history of the Cybermen, whether it's mentioned on Newsround, or a website, or mum and dad talking."

More than 10 million viewers tuned in to the Christmas episode of Doctor Who and, far from resting on his laurels, Davies is all too aware of the pressure of ensuring the new series continues to delight. He has insisted on up to 12 drafts of each episode in the new series and has had no qualms about rewriting other people's scripts. "I would have enormous reservations about doing that if this was a programme like Clocking Off, authored pieces in which people have something very specific to say about the world.

Then you should let the writer's voice flourish. This is unashamedly a piece of entertainment on a Saturday night, there to get mainstream appeal. I'm afraid all my principles fly out the window."

He is full of admiration for the designers and directors who realise his ideas, letting slip that the budget for each episode is "a significant third" less than the £1.2m reported because he feels it "makes a mockery of what people are doing". "It's the same budget as Waking the Dead, which is a lovely show, but it's all set in London, standing in offices and morgues and sitting in Rovers."

A lifelong fan of Doctor Who, Davies refuses to pander to others who share his addiction. He fears a lot of sciencefiction writers, particularly in America, pay too much attention to what is written on fan websites. "I think it's a huge mistake. If you came to me and said ?You've made a brand new programme, I'd like to run it past a focus group of 2,000 people, ' I'd say, ?No way, no good drama has ever been made that way.'" He has even less time for television critics, believing they fail to engage with television as popular culture because they watch shows like Doctor Who on a VHS tape on Tuesday morning, rather than at the point of transmission on Saturday night, making for a completely different atmosphere.

Davies was born in Swansea, and making Doctor Who and now Torchwood in Wales has been something of a homecoming after spending most of his career in Manchester. His breakthrough came in 1998 with Queer As Folk, the controversial Channel 4 drama about gay men living in Manchester, which he freely admits was closely based on personal experience.

"There are people who won't talk to me again after that.

Vince [the main character] does that speech about losing his virginity while watching The Two Ronnies. It's word for word what happened to an exboyfriend of mine."

Davies's career as a scriptwriter began with an apprenticeship at Granada, where his first job was on Children's Ward working under Paul Abbott, still a great friend, and Kay Mellor. He begged to write for Coronation Street, but is glad to have been turned down. "If they'd said yes I'd never have left."

Although his dramas have covered a dazzling breadth of subjects, the one theme running through them all is "writing impossible things". There is Bob and Rose, in which a gay man falls in love with a woman; The Second Coming, starring Eccleston as Jesus; and Mine All Mine, in which Griff Rhys Jones plays a man who inherits an entire Welsh town. For his next project, dubbed MGM (More Gay Men), Davies plans to return to the domestic arena of Queer As Folk. Nicola Schindler, doyenne of Manchester-based Red Productions, is waiting patiently until he finishes Doctor Who - he is signed up for at least two more series - to make the new drama, which will be "a bit more 40-yearold".

"I thought of Death in Venice.

Like any 40-year-old, you start to feel like 20-year-olds are an alien race. It will be on BBC1 hopefully. I'm quite aware that the BBC hasn't got a big gay series and should."

Entering his 40s has pricked Davies's conscience about his Welsh roots. He admits his first drama set in Wales, Mine All Mine, was a flop - "it died a death, a terrible disaster" - but says it has made him more determined to try again. "When Mine All Mine didn't work, there were a lot of people sneering, saying, ?Ah well, failed, that's the end of Welsh drama, you'll never get that on the network'. The solution is just to turn round and do it again."

He hopes to do just that with Torchwood, which is set in Cardiff in 2006 with a strong Welsh cast and crew - although there are also some English actors, including Burn Gorman.

"The more you can get that accent on screen, the more normalising it is, " he explains.

Is it an attempt to get more Welsh voices on to network television by stealth? He lets out another of his trademark huge guffaws. "It is a stealth campaign, " he agrees gleefully. "Stealth Welsh."