Ruth Jones: 'Gavin & Stacey generated a lot of warmth. It's good to warm your cockles'

Oh, what's occurring? The actress and writer Ruth Jones has been quite taken aback by the extent to which this catchphrase from her hit sitcom Gavin & Stacey has caught fire. A fan-site on Facebook called "Oh! What's Occurring?" boasts some 30,000 members, while people are using Jones's memorable rendition of the phrase as a mobile ringtone. She is constantly stopped in the street by strangers chanting it at her. As Nessa, her character in the series, would put it: tidy.

In BBC1's Gavin & Stacey, which Jones co-writes and co-stars in with James Corden, the very conventional title characters – Essex man Gavin (Mathew Horne) and his beloved Stacey (Joanna Page) from Barry Island – are in theory the leads. But in practice, the figures who steal the show every single week are their highly idiosyncratic best friends, Smithy (Corden) and Nessa (Jones).

Nessa, in particular, has built up an impressive cult following. A compelling comic creation, this denizen of Barry Island's pubs, clubs and the arcade (where she works) has really captured the public imagination. Viewers relish her invincible self-confidence, her unique use of language and her fantastically casual attitude to sex. And then there's Nessa's astoundingly colourful past. Rumours of a liaison with Nigel Havers just won't go away, and she admits at one point that, "if it wasn't for my relationship with John Prescott, I'd probably still be in that jail". There were also her three trips round the globe as a deck-hand, her time in All Saints – before a big bust-up with Shaznay – and a shady period when she did unspeakable things with Mars bars in Amsterdam.

Female columnists trumpetNessa as the new role model for women in the 21st century. She's clearly the sort of real, non-rake-thin woman that people can connect with. To underline the character's authenticity, the real-life amusement arcade in Barry is bombarded with so many people wanting to meet her that it has put out a sign which reads, "Nessa is not working today."

Nessa has also helped to catapult Jones into the big league. Since breaking through in Gavin & Stacey two years ago, the actress has landed an impressive array of parts, from Joan, the heroine's grasping mother, in Tess of the D'Urbervilles, to Flora, Arthur Clennam's lovelorn ex, in Little Dorrit. Now she's taking her bow in The Street, the outstanding series of BBC1 single dramas written by Jimmy McGovern (Cracker, The Lakes, Hillsborough). The series is shot on meticulously created sets at a studio called the Pie Factory in Manchester. After filming, Jones and I talk, and the conversation wanders down The Street and far beyond. "I love the fact that I'm getting such variety now. It's a huge compliment to be seen as a dramatic actress and not just a comic actress," says Jones who, off-screen, is as bashful as Nessa is brazen. This appealingly shy, self-effacing and softly spoken actress is the polar opposite of the stereotypical, exhibitionist, "look at me" performer. Even her clothes are understated – you wouldn't catch Jones in any of Nessa's out-there PVC gear.

In The Street, Jones plays Sandra, a lonely minicab controller. She falls for her colleague, Eddie (Timothy Spall), despite the fact that he is married to the long-suffering Margie (Ger Ryan). When Eddie succumbs to Sandra's advances, their liaison has drastic consequences. "It's not happy ever after for either Sandra or Eddie. They are both forced to reassess their lives", says Jones. "In Jimmy's work, there are always consequences. He has a real knack for depicting anti-heroes and locating the heroic in a non-hero. Jimmy throws you in at the deep end with a character, and yet you instantly know where you are."

The double-Bafta-winning drama, which is now entering its third series, also affords access into what may be occurring, unbeknownst to us, right next door. "The Street is an excellent precinct for a drama because no one truly knows what goes on behind closed doors in any particular road," says Jones. "We all put on very different faces in public and in private."

Jones's own private life is fairly quiet. The actress, whose father was a legal executive for British Steel and whose mother was a doctor, hails from Porthcawl. She now lives in Cardiff with her producer husband David Peet and has three grown-up stepchildren, Fiona, Louise and Alex. She met Peet on a comedy pilot in the early 1990s and now runs the aptly named Tidy Productions with him. They made her BBC Wales radio chat show, Ruth Jones' Sunday Brunch, and have several other productions in the pipeline.

For now, she's concentrating on making the eagerly anticipated third series of Gavin & Stacey. She first met her co-creator Corden while working on four seasons of the ITV1 drama, Fat Friends. They soon realised they shared a sense of humour and were urged by then BBC3 controller Stuart Murphy to write Gavin & Stacey after showing him just a few pages of outline ideas.

The co-writers are very different – she a 42-year-old wife and mother based in Cardiff, he a 31-year-old unmarried London man about town – but perhaps it's that very difference that helps them remain so close. They both say that their friendship always comes before everything else. "James and I often don't see each other for long periods – we're both so busy – but we have always had this great chemistry."

Jones is delighted to be back in Nessa's knee-high boots again. "People love her," she says. "Some see her merely as an old slapper, but I don't think she's that easy to define. She's actually a very strong-minded person. She has a heart of gold and will always defend her friends in a fight. And she has this self-assurance that's very attractive. Nessa's a huge enigma who has led this life you can't believe. There's this wisdom about her that people are drawn to. She's deeply philosophical, a Barry Buddha."

So do the actress and her alter ego overlap at all? Jones gives a self-deprecating laugh. "There's very little of me in her. I wish I was more like her. I worry all the time about what people think of me, but Nessa doesn't care at all."

In fact, it seems as if there are still some striking similarities between Jones and her fictional creation. Like Nessa, the actress has lived a bit and has something to say for herself. She offers the world a wise, witty personality, rather than the vacuous twitterings of a twentysomething model. And how refreshing to meet someone who has become a star after passing the age of 40.

All the same, Jones remains astonished by the way in which Gavin & Stacey has taken off. The series has won two Baftas and four British Comedy Awards – unheard-of accolades for a show that debuted on BBC3. The weirdest by-product of the show's success is that total strangers now think that they know her. "I was on a train the other day, and the man sitting opposite me said, 'Hi, Ruth, how are you? Well done at the Comedy Awards. What are you up to at the moment?' What was really embarrassing was that at that moment, I was checking something on the Gavin & Stacey DVD. I'm normally very careful to hide it, but this time it was blatant. The bloke saw it and asked, 'Watching your own programme, are you?' It looked like self-glorification city."

That is not where Jones dwells, though. Even after such acclaim, she remains rather abashed, almost embarrassed about her success. "I still can't get my head around it. Whenever someone asks for my autograph, I still think, 'Do you really want it?' I'd never take it for granted – God, no! My default setting is 'they don't really like me'."

Gavin & Stacey has continued to do attract the good wishes of complete strangers in part because it's a response to the prevailing trend for comedies that are blacker than a raven's wing. Gavin & Stacey very much falls into the category of "nice-com." The actress, who had a big hit for Comic Relief earlier this year performing "Islands in the Stream" with Tom Jones and her Gavin & Stacey co-star, Rob Brydon, agrees. "It wasn't as deliberate as us saying, 'Right, we're going to react against cynical comedy'. We just wrote what we wanted. And it just so happens that the show does generate a lot of warmth. People seem to like that, especially when things aren't terribly jolly. It's nice to have your cockles warmed."

In contrast to many comedies that leave a bitter taste in the mouth, "the characters in Gavin & Stacey do like each other", continues Jones. "Every day you read these awful stories in the papers that make you want to weep. You think, 'Why has this happened?' But at the same, people can also be lovely to each other. They like their families and friends. We think there's humour in that – it doesn't have to be nasty to be funny. James and I hope that we have created something that isn't cynical. Steve Coogan [whose company, Baby Cow, makes Gavin & Stacey] said that he really liked the show because it's about people laughing together. Nobody is the butt of the jokes."

The series underlines that people are naturally funny. "We are often hilarious without even realising it," reckons Jones, who has also had roles in East Is East, Saxondale, Nighty Night, Torchwood and appeared in Little Britain as Myfanwy, the down-to-earth barmaid always puncturing Daffyd's (Matt Lucas) claims that he is "the only gay in the village".

"The other I day I was talking to a friend's dad, who never swears at all. Then out of the blue, he said, 'That's just a load of bullshit.' He didn't even realise he'd sworn. On Gavin & Stacey, we aim to capture nuances of character like that."

Gavin & Stacey has also helped contribute to the sense that Wales is a creative hotspot right now. "Wales is on a real high at the moment," asserts Jones, who studied at Warwick University and the Welsh College of Music and Drama. "Our rugby team have won two Grand Slams in four years, we [BBC Wales] make Doctor Who, and the music coming out of Wales is terrific. We've got Duffy, the Manic Street Preachers, the Stereophonics, and Tom Jones. He's nearly 70 and he's just made a brilliant album. I hope Gavin & Stacey is part of that boom."

The actress is also hopeful that the series overturns some of the more egregious stereotypes about her country. "I'm very proud of the fact that we have a Welsh flavour without playing up to that boisterous Welsh image. I don't like the clichéd portrayal of the Welsh on TV – that thick, unlikeable, sing-song accent and everyone saying 'boyo' all the time. I think we've dispelled that."

Jones looks back with justifiable satisfaction on the last 12 months. "What a year," she beams. "It's been absolutely incredible. To have done a Charles Dickens, a Thomas Hardy and a Jimmy McGovern all in one year is great. It feels like an Oscar Wilde line: to get one would be considered a joy, but to get three is positively delirious. I'm really chuffed."

Then, all of a sudden, Jones's default vulnerability setting kicks in again. "But who knows? That may never happen to me again. I'm a fussy bugger, though," she adds with a smile. "So I don't want to go away for a while yet."

Jones is talented enough to be around for quite some time yet. She is also very canny, well aware that the greatest enemy to her longevity may be over-exposure. "I hate the thought of people saying, 'Oh God, not her again!' So now I'm going to be quiet for a bit. I'll emerge in a little while like a tortoise coming out of hibernation."

'The Street' begins on BBC1, 13 July at 9pm