TV’s funniest woman: Ruth Jones on life after Gavin & Stacey

Ruth Jones is surprisingly petite in the flesh, which may seem an unpleasantly size-ist, not to say ungallant, observation to make at the top of an interview, but then Jones has made a career out of playing larger ladies. Her breakthrough came in an ITV series called Fat Friends, her Nessa in Gavin & Stacey was outsize and proud, and in a new BBC4 biopic she is playing Hattie Jacques, the statuesque foil to so many weedy Carry On men.

Hattie, based on Andrew Merriman's 2007 tome Hattie Jacques: The Authorised Biography, focuses on the comedy legend's affair with a much younger man, car-dealer John Schofield, a relationship that led to the break-up of her marriage to comedy actor John Le Mesurier (later and most famously to be Sergeant Wilson in Dad's Army) – but not before cuckolded husband and new lover had shared a house together. Jacques's co-star on the long-running TV sitcom Sykes, Eric Sykes, recently criticised the BBC4 drama, saying that "it's very sad that parts of her life are being raked over".

Jones, however, sees it differently, saying. "She [Jacques] herself said in an interview, 'if you're fat you're funny and it's as simple as that' – so it's good, I think, to see the person behind this funny fat-woman role.

"I read the book, which gave me quite an insight. She had quite a passionate liaison with an American officer during the war. I suppose the public persona that she put out was not one of this sexy, passionate woman, but she was a really beautiful woman and had an incredibly interesting face and had a real warmth about her."

Hattie may disappoint those hoping to see variations on Jacques's Carry On persona, or Ruth Jones in full-on Gavin & Stacey mode.

"There's not really a lot of laughs in there at all", she says. "If you want to watch the comedy then watch the comedies these people are in, if you want to know the real lives then the real life will have tears in it."

And Hattie begins with its heroine in tears, on a hotel bed in Rome in 1966 after Schofield (played by Aidan Turner, from Being Human) has announced that he is leaving her. Three years earlier Jacques had been 40 and at the height of her career, busy filming Carry on Cabbie, when she met the married Schofield, a cockney rough diamond on the verge of leaving his wife, after he wrote inviting Jacques to become patron of the Leukaemia Research Fund (his then two-year-old had contracted the disease).

As detailed in Merriman's biography, there followed a most peculiar ménage in the chaotic Earls Court home – Schofield playing with Jacques and Le Mesurier's two children while it slowly dawned on the somewhat aloof Le Mesurier what was going on under his roof. Desperate to save his marriage, the actor persevered with this humiliating domestic arrangement until he snapped when Schofield moved into the marital bed and he was relocated to a loft room. Family friend Bruce Copp introduced Le Mesurier to Joan Mallin, a 33-year-old clerk who worked in the evenings behind the bar at the Queen's Theatre in Shaftesbury Avenue and, encouraged by Hattie, they began dating. At Christmas 1964, more than a year after Schofield had moved in, Le Mesurier packed his bags – remarrying in 1966 having first admitted to adultery in order to save Jacques's reputation.

"The redeeming part of the real-life story is that they [Jacques and Le Mesurier] did remain friends", says Jones. "But it's a terribly sad story because, of course, she does end up on her own".

The only link to Hattie Jacques with whom Jones had contact was Joan Hancock, Tony Hancock's widow. "She was great and came up with this great phrase when talking about Hattie and John Schofield – she said that Bruce Copp used to call them 'Mr and Mrs Lucky Fucky'.

"The impression I got from the book about Hattie was that she did put up with quite a lot of prejudice about her size, but she seemed to take it with good grace. Why should she take it in good grace I don't know, but she did, so it was good to talk to someone who knew her as a person, as a friend, rather than this funny fat lady."

Did Jones, another "funny fat lady" (she doesn't demur at this description of her), empathise at all with Jacques – a woman made more vulnerable to Schofield's flattering advances by insecurity over her weight?

"I don't want to make generalisations here, but I think that most women and maybe men are not comfortable with being overweight", she says. "It's a tricky issue."

Jones's own domestic arrangements are more straightforward – she lives in Cardiff with her husband, TV and radio producer David Peet, and his three grown-up children from an earlier marriage. Together they have created Tidy Productions ("tidy" as in its Welsh meaning of being good).

"I love Cardiff and love living in Cardiff – you don't have paparazzi in Cardiff", she says. " I do get stopped sometimes, and one time quite embarrassingly in the supermarket when I decided to fill up on toilet rolls and had two 12-packs..."

She was born 25 miles around the coast, in the Welsh seaside town of Porthcawl, her father a legal executive at British Steel in Port Talbot and her mother a GP turned child psychiatrist. None of her family are thespians, although she was at school with her future Gavin & Stacey co-star Rob Brydon. After studying drama at Warwick University, she spent the next 20 years becoming the "the best comedy newcomer" at the 2007 British Comedy Awards.

Jones has often blamed her lack of self-confidence for her being such a late developer. "All my life I've had this belief that other people are better than me", she said last year. "It's only now that I'm starting to realise I'm alright, that I'm not bad at what I do." Not bad at all – in fact these days she is roundly hailed as one of the funniest – perhaps the funniest (see our list of her competitors) – comic actresses of her generation.

Indeed the slow rise to the top may have actually been a blessing in disguise – and whether it has been the long years on the periphery of comedy's charmed circle that robbed her of a comedian-sized ego, traditionally the biggest and most brittle of the lot, or whether she was just born that way (I suspect a bit of both), she is genuinely unassuming. That might have been why she has been overlooked in the past, or used as other people's comic foil – Matt Lucas's or Steve Coogan's – but now at last there is a sense of a writer and performer who has grown into herself. She now knows what she's worth. If she can sustain this new-found self-belief then she could be the next Victoria Wood, and while the age of 44 is advanced in years to earn that accolade, it's thankfully not too late.

And there is another quality you can't fake– something she shares with Hattie Jacques – and that's, however cartoonishly or monstrously she might be behaving, there is always an underlying warmth in her performances (and in her writing) and audiences respond to it. Gavin & Stacey's Nessa could be – indeed often was – the most downbeat of deadpan characters, but she never once seemed to alienate viewers. "She has a real soft side to her, Nessa," agrees Jones.

But is has been a slow climb to recognition. After an eye-catching turn as a gobby northerner in the 1999 film comedy East is East, Jones was cast as Kelly, an overweight blonde from Leeds, in four seasons of ITV's slimming-club saga Fat Friends, which is where she met her future Gavin & Stacey co-writer James Corden. Roles followed in Julia Davis's BBC3 black comedy Nighty Night before she played Little Britain's Sapphic barmaid Myfanwy – the constant living reproof to Daffyd's boast of being the only gay in the village.

Myfanwy was little more than a cameo however, while Magz, Steve Coogan's long-suffering girlfriend in his BBC2 sitcom Saxondale, evolved into something of a thankless role. But by then she was already writing, along with James Corden, the first scripts for what was going to be the great game-changer, BBC3's Gavin & Stacey.

"Before Gavin & Stacey I'd won a BBC short-story competition", she says, "And when I was working on Fat Friends I wrote an episode". But nothing could have prepared her for the success of her warm-hearted comedy about a girl from Barry (Joanna Page) who falls in love with a boy from Essex (Mathew Horne).

Jones and Corden have both categorically ruled out any future episodes of Gavin & Stacey, although Jones appeared to be relenting last September when she told a reporter that, "a lot of it is to do with logistics, because we haven't ruled out doing a special at some point in the future". How many times a day does she get asked about whether there would be any more Gavin & Stacey", I ask her. "That's first time today", she deadpans.

And anyway, she is busy finishing scripts for Stella, her production company's new ten-part comedy drama for Sky 1 about a fortysomething mother facing problems with life, love and her neighbours, "an authentic slice of the working-class Welsh valleys," in which Jones will take the title role.

And if you can write your own material, and it's good, you are always going to be at a great advantage. Unwittingly or not (she claims it was unintentional) Jones and Corden fed the best lines in Gavin & Stacey to their characters, Nessa and Smithy – Nessa providing some lovely moments of pathos along with the catchphrases ("Oh, what's occurrin'" and "I not gonna lie to you") as well as the necessary caustic counterweight to Gavin and Stacey's lovey-doveyness.

The dividends have been enormous. This Christmas she seemed as ubiquitous as Ronnie Corbett, fronting her own chat shows (Ricky Gervais and Miranda Hart were guests), starring in an adaptation of Dylan Thomas's A Child's Christmas in Wales and a repeat of last year's Gavin & Stacey special, while her sitcom about a rambling club, The Great Outdoors, has just started a re-run on BBC4.

And at an age and of a shape that has confined many a fine performer to character parts, Jones is, rather wonderfully taking the lead. After supporting roles in Tess of the D'Urbervilles, where she played the mother of Gemma Arterton's Tess, and in BBC1's Little Dorrit, Hattie marks her first lead role in a drama.

"My ambition is always to play parts that are different and are a challenge", she says. "However you have to be realistic and I know that I'm never going to play Juliet... I will probably always play the nurse."

The other danger with a winner like Gavin & Stacey is the curse of typecasting. "I've been very lucky so far", she says. "I can't say people are knocking down my doors to play overweight Barry girls, because they're not".

Are there any real-life people she would like to play after Hattie Jacques? "Maybe Lauren Bacall," she says after some consideration. "But I would have to lose a bit of weight for that".

'Hattie' is on Wednesday at 9pm on BBC4

FUNNY WOMEN: QUEENS OF TV COMEDY

Miranda Hart

Hart's BBC2 sitcom 'Miranda' looks set to sweep the British Comedy awards next weekend as the 6ft1in comedian brings slapstick back into the nation's living rooms. Like Ruth Jones, the 38-year-old Hart is another decade-long 'overnight success', having appeared in roles in 'Smack the Pony', 'Absolutely Fabulous', 'Nighty Night', 'Hyperdrive' and 'Not Going Out'.

Rebecca Front

Front's long apprenticeship began with Steve Coogan in 'Knowing Me Knowing You with Alan Partridge', continued with Coogan, Chris Morris and Armando Iannucci in the seminal 'The Day Today', and has recently flourished via Nicola Murray MP in 'The Thick of It' and Simon Amstell's mother in 'Grandma's House'. And Front still finds to play Kevin Whateley's boss in 'Lewis'.

Sharon Horgan

'The funniest woman you've never heard of,' is a tag that has stuck with the Irish comedy actress Sharon Horgan, who, like Ruth Jones, has written her own best roles. The outrageous black comedy 'Pulling' was the sitcom that earned Horgan a cult following, along with 'Angelo's' and 'Free Agents'. Horgan's most recent work has been in More4's US/UK sitcom 'The Increasingly Poor Decisions of Todd Margaret'.

Tamsin Greig

The Dylan Moran sitcom 'Black Books' provided Tamsin Greig with her big break, but her career really took off opposite Stephen Mangan in Channel 4's improvised hospital-comedy 'Green Wing'. She is currently reunited with Mangan in BBC2's 'Episodes', playing married British TV writers having to cope with star Matt LeBlanc and creating a Hollywood remake.

Julia Davis

Ruth Jones, Rebecca Front and Miranda Hart all had roles in Julia Davis's pitch-black sitcom 'Nighty Night', which Davis wrote, while she has been a regular collaborator with Chris Morris, most recently on his film 'Four Lions'. She started out as part of a comedy troupe that also included her future 'Gavin & Stacey' co-stars Rob Brydon and Ruth Jones.