Ever wondered what Carry On actress Hattie Jacques might've looked like in the throes of sexual ecstasy? Then look no further than BBC 4's latest "tears behind the laughter" biopic, hattie, which takes a mildly scurrilous peek at a peculiar episode from her once private life.

Though hidden from the public during their lifetime, it's now common knowledge that Jacques and her husband, beloved British comedy actor John Le Mesurier, were embroiled in a bizarre love triangle involving cockney chauffeur John Schofield.

The film shows how Jacques was seduced by this ravishing charmer, who then moved into her marital bed while Le Mesurier - in an almost farcical display of gentlemanly English stoicism - was banished to a guest room.

Jacques obviously adored her husband, so what was she thinking? Unfortunately, writer Stephen Russell doesn't provide many answers beyond suggesting that, insecure about her weight, she was flattered by the attentions of a younger man. It all feels rather glib.

Though Schofield (Being Human's Aidan Turner) is depicted as having genuinely fallen in lust with the vivacious actress, Russell also suggests that the material trappings of her celebrity lifestyle proved just as enticing.

As for Le Mesurier, he's portrayed as an exasperating cuckold incapable of functioning without his wife's support. The public humiliation he avoided in life is now exposed for all to see: hardly the point of his sacrifice.

Ruth Jones is fine in the lead role, although she doesn't have much to work with. Maybe Jacques really wasn't that complex in real life, but there must have been more to her than these superficial character traits. She's depicted as warm and charitable, with a girlish sense of fun, but an immature recklessness when it came to her own family. And that's it.

Robert Bathurst steals the acting honours as Le Mesurier, suggesting acute sensitivity beneath those famously vague mannerisms. But his character never really comes alive either.

Although not bad as such, Hattie suffers from rather bland execution. It recounts a strange, voyeuristically interesting story, but rarely engages on an emotional level.

Ruth Jones on life after Gavin & Stacey

The writer and star of Gavin & Stacey is adding Hattie Jacques to her list of acclaimed creations. Gerard Gilbert meets the late-blooming comedian.

Eric Sykes hits out at Hattie Jacques drama

Veteran actor and writer Eric Sykes has criticised an upcoming TV drama about friend and colleague Hattie Jacques.

The actor and writer Eric Sykes, with whom Hattie Jacques had an enduring partnership on television, once described the matronly comic actress as "one of the very best". She was also referred to as the "Mother Superior of the Carry On family". This repeated profile, with contributions from Sykes, Miriam Margolyes and Mo Mowlam, looks back at Jacques's life and career in television and film, and at the sad fact that her talents as a straight actress were often overlooked because, as she lamented, directors only gave her "funny fat lady" parts. A new drama about Jacques's life, Hattie, airs on BBC Four on Wednesday, January 19.

Ruth Jones interview

With a new comedy series and a chat show up her sleeve, plus a starring role as the Carry On actress Hattie Jacques, Ruth Jones is as busy as ever...

Is this the funniest woman in Britain?

She's as comedic as Tommy Cooper and as hilarious as Hattie Jacques. Now Miranda Hart has won the affections of Allison Pearson.

How to describe Miranda Hart's style of comedy? Certainly, she throws everything into it - panto, slapstick, a little social satire, bad singing, malapropisms, farting. Whatever works. Of course, the biggest thing she throws into it is herself. And if she lands on her backside, well, hey - job done! The second series of Miranda started as her fans hope it means to go on, with a taxi whipping off her party dress and roaring away with it caught in the door. Magnificent.

If this had been the Carry On team, they'd have chosen saucy little Babs Windsor to be stranded in the street in her smalls. I'm not suggesting that Miranda is more of a Hattie Jacques, but oh lordy how much funnier - and she knows it - to have a woman of size lumbering up the street in bra, big pants and unattractive tights, valiantly putting art ahead of dignity.

Do women mind that men would find that such a hoot? It seems safe to assume that Miranda's constituency is vastly female, though her overarching rom-com plot - the perennial pursuit of Gary from the local gastropub - is merely a slave to Miranda's primary purpose of making a show of herself. But what a show! Listen to that live studio audience - a pit of hyenas feeding on their own laughter. More! More!

Sometimes, it was the mock-heroic way she told 'em ("I am with much news that I shall now birth!"); sometimes, a cheeky aside to the camera did the trick, or even a simple ungainly twirl. No one cares where the laughs come from, but come they must and do. Miranda's higgledy-piggledy castle of fun is built on instinct rather than theory.

The show cloaks itself in wholesome, old-fashioned japery with its broad misunderstandings ("I said ghosts, not goats!") and knowing winks at Hi-de-Hi! and Frank Spencer, and the way Miranda's mother (Patricia Hodge) flits in and out as if through a time portal to a 1950s Whitehall farce.

But there's always a sharp sensibility at work - in Hart's gleeful observations of Miranda's post-Bridget Jones victimhood, of the girly fads and shibboleths ("Fabulasmic!") of her fatuous posh friends - and if anyone is more hilariously note-perfect at being one than Sally Phillips (who is literally a scream as the hyper-amused Tilly), I'd hate to meet them. So, yes, more.

Ruth Jones as Hattie: are you enjoying biographical TV?

The Gavin & Stacey star is to play comic actress Hattie Jacques in the latest biopic for BBC4.

Hattie Jacques and Her Heartbreak

Nor long after the end of the war, a young Eric Sykes visited the Players Theatre, a venue under the arches of Charing Cross Station in London that specialised in old-style variety entertainment. The show was nearing its end when the master of ceremonies banged his gavel to introduce a performer who would captivate the budding comedy writer.

Ruth Jones to play Hattie Jacques in BBC biopic

Ruth Jones, the Gavin And Stacey star, will play Hattie Jacques, the Carry On comedy legend, in a BBC biopic.