Julia Davis: 'I don't want to offend anyone'

She made her name playing monstrous comic characters in the likes of Nighty Night, Gavin & Stacey and Human Remains – and her latest project is a twisted period drama. Surprising, then, that Julia Davis turns out to be the shy, retiring type.

Neither Julia Davis nor her PR seem to have noticed that we have been booked into Room 101 at London's Soho Hotel for our interview, the Orwellian aptness being that Davis would probably place talking to journalists higher on her list of personal dreads than being devoured by rats (some might argue that they are the same thing).

Anyway, she has given precious few newspaper interviews, and doesn't do TV chat shows. "I always imagine people give succinct answers," she explains. "I have no prepared thoughts on what I do."

The irony is that Davis does give succinct answers, delivered in a soft, clear voice accompanied by a radiant grin that gets wider and toothier in the silence that follows her succinct answers, as if to make you feel complicit in the understanding that this whole publicity rigmarole is all rather ludicrous. She's shy, but bashfulness doesn't get more beguiling than this. "It's an odd one because I really enjoy watching other people [on chat shows]," she says, "thinking 'I wonder what they're really like?'."

What Julia Davis is really like is a moot question that will have intrigued anyone who has witnessed her monstrous comic creations – mostly famously, the sociopathic beauty-parlour owner, Jill Tyrell, from her BBC2 sitcom Nighty Night, a woman apparently based on one of Davis's erstwhile colleagues when she worked in a finance department in a university. "There was a lady there who was really blunt and quite rude," she says. "I'm not saying it was all her… I mean, I've been to hairdressers who've been a bit like that."

The two series of Nighty Night were a hilarious vortex of ever-increasing tastelessness, as Jill, upon learning that her husband, Terry (Kevin Eldon) has cancer, tells everyone that he has died – locking him in their bedroom in a nappy after he makes a recovery, before eventually smothering him with a pillow. It's hard to square such dark and twisted comedy with this softly-spoken woman sitting here in Room 101. But then, it's always the quiet ones…

"It's probably a reaction to being, in life, quite censored, so it's a chance to not be," she says. "Like Larry David and the way people think he's like his character in Curb Your Enthusiasm and he always says he'd never say any of those things. And Chris Morris – he's so not like that; he's really nice."

Morris, along with Rob Brydon and Steve Coogan, have been important comedy partners and influences, but more of them later. Because, after several years out of the limelight (or what passes for limelight in Davis's publicity-averse world), which she has largely devoted to bringing up her twin sons (five-year-old Walter and Arthur), Davis is back with a brand-new self-penned comedy, Hunderby.

Set in 1831, Davis plays Dorothy, the forbidding, Mrs Danvers-like housekeeper of a widowed vicar, Edmund (Alex MacQueen from The Thick of It), who has just married Helene, a mysterious young woman found shipwrecked on the beach. It's a wonderful pastiche of a Gothic melodrama absorbing multiple influences, from Thomas Hardy to Rebecca and the films of Bette Davis. "I love all Daphne du Maurier's stuff," says Davis. "And just enjoying period dramas really… wanting to do something drastically different from Nighty Night, the chance to write very different language."

It's all played admirably straight, much of the comedy stemming from the juxtaposition of the ornate language and what the characters are actually saying – a period drama with snatch jokes, in other words, and one in which Edmund, on his wedding night, could compare Helene to his late wife: "Nature did not busy her broken mound with such a black and forceful brush". "I can't say who it would appeal to," says Davis. "I can't say whether the people who watch Downton Abbey would enjoy watching that…"

It's interesting that Hunderby should have been made for Sky Atlantic. Was this a reaction to the way that the BBC treated her most recent comedy, Lizzie and Sarah? Despite being written with and co-starring that other cult comedy heroine, Jessica Hynes (most recently PR Siobhan in Twenty Twelve), Lizzie and Sarah, a bleakly funny tale of spousal abuse, was broadcast at 11.45pm. And, despite some heavyweight Twitter outrage led by Simon Pegg and a 'Commission Lizzie and Sarah' Facebook campaign, it never went beyond the pilot stage.

"Not in some sort of flouncy way," she replies. "I just felt that the stuff that I'm interested in wasn't necessarily appealing to what they [the BBC] are doing at the moment. It's just a question of going somewhere where you're wanted." And that includes Channel 4, which is showing the pilot episode of Bad Sugar, a spoof telenovela written by Peep Show's Sam Bain and Jesse Armstrong. As part of a dream female cast including Sharon Horgan (Pulling, Dead Boss) and Olivia Coleman (Peep Show, Rev), Davis plays the daughter of a mining magnate and yet another dark and twisted bitch. Is this the real Julia Davis?

"No, not in my life," she smiles sweetly. "I don't think any of my friends or children would think that. But I never seem to have an answer for it, though… I guess it's like music or art or anything – you just do what comes out and you don't really know why."

Certainly there's nothing in Davis's "pretty average kind of upbringing" to explain her choice of style and subject-matter. "My dad was a civil servant and my mum was a secretary," she says. "I was brought up in Guildford and I think I used to absorb all the suburban things – seeing coffee mornings, women talking… that stuff really. I was watching Alan Ayckbourn on some documentary and he was talking about how he was around a lot of women as a child, listening to all that stuff."

At school in the home counties and Bath (where the family settled when she 14), she wasn't the classic class clown. "I was the same as I am now, in that I'd always have a quite small group of close friends who might say I'm funny," she says, "but I'm not the show-offy type."

Religion tends to play a significant role in her comedies – Jill in Nighty Night is a member of a church group, while the heroine of Hunderby is married to a pastor. "My mum's father was a vicar and my uncle is and I did go to church a lot and I was confirmed," she says. "It's a tricky area and I don't want to offend people… not in real life I don't. I'm not anti-Christian or anything like that. I do like everything that Jesus stood for, but for me personally going to church isn't where I feel that sense of spirit."

Davis once suggested any "darkness" might have stemmed from the two years in which she should have been enjoying being a student – studying English and drama at York University – but was instead laid low with glandular fever. "I always wonder," she says. "It was a very difficult time to be out of life because I was loving becoming independent, so it was really odd to go back home and be very introverted."

After graduation and assorted odd jobs she joined a West Country comedy troupe that included Rob Brydon and Ruth Jones – her future co-stars on Gavin & Stacey. "Rob was always very confident," she says. "He was already doing lots of voiceovers and also working for QVC – he won't mind me saying…"

Davis was then teamed with Arabella Weir and Meera Syal on a Radio 4 series called Five Squeezy Pieces – work noticed by Graham Lineham and Arthur Matthews, who chose her as one of the regulars on their seminal TV sketch show, Big Train, along with Chris Morris ("I thought, 'Who's the posh bloke?' It was Chris"), with whom she'd later work with on his controversial Channel 4 series, Brass Eye.

Meanwhile, having sent a videotape of her material to Steve Coogan, she was invited, along with the then unknown Simon Pegg, to join Coogan's stand-up tour in 1998. But it was with Brydon that she had her first big breakthrough, in the cult BBC2 comedy Human Remains, a series of two-handers that won a small but devoted audience. "Rob is one of the most enjoyable people I've worked with," she says. "It was just an easy way we created stuff together, just by improvising and then writing it down."

In between, there have been small film parts – in Love, Actually, a film she once claimed never to have watched, although she looks bemused when I re-read that statement to her now, Ricky Gervais's Cemetery Junction and in Chris Morris's Four Lions – as well as straight acting roles, as Fanny Craddock in BBC4's Fear of Fanny and The Alan Clark Diaries. She'd like to do more, but admits: "I'm not great at auditions. I'm beginning to see now – getting people in for casting Hunderby – some people are incredibly good at selling themselves. I'm not, no…"

She has in the past linked this lack of confidence to depression. How serious is it? "Not in the sense where I literally can't get out of bed," she says. "I don't feel I need to be locked away or anything, it's just a general tilt in the direction of… All I think is 'Thank God for my sense of humour'."

She has rejected therapy, saying that, "You're paying someone, so they don't really care about you," but now says she might try cognitive behavioural therapy. "Because that's very 'Try this, do this', as opposed to sitting and… For me, the more I sit and talk about what's worrying me, the worse I feel." Having a family has also helped. "Obviously children are a great way to be happy," she says. "You just can't afford to be sitting around and wallowing."

Has motherhood tempered her choice of material? "I don't think it has. I don't think, 'Oh I mustn't write that sort of thing now because I've got children'. Obviously I don't want them to see it now, but one day they might." And I can't help cringeing at the thought of young Walter and Arthur witnessing mummy's antics as Jill in Nighty Night. Kids, after all, access YouTube at a scarily early age these days. "I'm such a technophobe, I try to keep them away from all that," she says. "I think they've got a while yet before they look at all that."

Davis may spending time with her children, but she doesn't like to work from home, preferring instead her local café in north London. "I like sitting with lots of people around," she says, "that sense of not being isolated." But don't people recognise her all the time? "A little bit, but not much," she says. "'Hiya Cath!' [Jill's clarion call to Rebecca Front's MS-suffering neighbour in Nighty Night]… I get a lot of that. Cab drivers, it's always Gavin & Stacey; gay men, it's Nighty Night."

The father of her twin sons is Julian Barratt – one half, with Noel Fielding, of surrealist comedy duo The Mighty Boosh. Barratt is famously shy, and the moment I took against Jonathan Ross was during what I considered to be a rather bullying interview on his BBC1 chat show, an occasion Barratt clearly was not enjoying. "He's not dissimilar to me," says Davis when I tell her this. "He's not comfortable in that environment."

And on the subject of diffidence, now for the bit she really hates – having her photograph taken. I can tell that she's being made self-conscious by the experience, not because of the repeated suggestion by Rick the photographer that I should keep her distracted with more questions, but because all I can now see of Davis with my myopic eyesight is her dazzling smile. And it's getting bigger and bigger and bigger and bigger.

'Hunderby' begins on Sky Atlantic on Monday; 'Bad Sugar' is on Channel 4 tomorrow