Friends like these: The BBC is hoping that its new series 'Mutual Friends' will match the success of'Cold Feet'

The new Cold Feet: it's one of those holy grails of the schedules. After numerous not very successful attempts to follow in the comedy-drama's footsteps (Hearts and Bones, Big Bad World or Metropolis, anyone?), maybe this time the commissioners have unearthed that holiest of holies – the middle-class serial that mirrors the lives of its viewers. Mutual Friends certainly has more than a touch of Mike Bullen's hit show, which ran for five seasons from 1997, about it.

Scripted by Richard Pinto and Anil Gupta, previously responsible for The Kumars at No 42 and Goodness Gracious Me, this new BBC1 six-parter centres on a group of late-thirtysomething lawyers and business executives: Martin (Marc Warren from Hustle), Jen (Keeley Hawes, Spooks), Patrick (Alexander Armstrong, The Armstrong and Miller Show), Liz (Sarah Alexander, Coupling) and Carl (Alistair Petrie, Cranford).

The drama starts at the moment when the roof caves in on Martin's world. His best friend, Carl, commits suicide, and Martin's wife, Jen, picks the occasion of the funeral to confess to him that she has been having an affair with Carl. In the following days, Martin is estranged from his wife and adored son, Dan, infuriated by the irresponsible behaviour of Patrick and on the verge of being sacked from his job as a lawyer. As Martin is reduced to ever more desperate measures to stop his universe disintegrating completely, he cries out: "What happened to us, eh? How did we get here?"

Later, he implores Jen not to leave him. "I thought we were happy," he cries. "Nobody's happy," she replies in a phrase that rings through the drama. So far, so Cold Feet.

But Rob Bullock, the producer of Mutual Friends, is anxious to avoid the C-word. "Cold Feet is about a different period of life. It's about people in their early thirties. Mutual Friends moves things on – what's happening to our characters as they approach 40 is very different. Why do so many lives fall apart at 40? Because things haven't worked out how we hoped and we've had to turn to Plan B. The drama is all about the crisis caused by things not turning out as the characters planned."

Bullock, 38, says: "People will really relate to Martin. He works very hard and worries all the time about providing for his family, but however hard he paddles, he never feels like he's getting anywhere. Then, when his wife reveals she's had an affair, his world unravels. He is overwhelmed by a sense of anger at the injustice of it all: 'I've played everything by the book, and yet this has still happened to me?'"

The producer, who also made Wild at Heart and Monarch of the Glen, continues: "This is very much not the world of the American series thirtysomething, where everyone is a smug, high-achieving yuppie with a perfect life."

Bullock adds that the plush setting – in affluent Henley-on-Thames – is deliberate. "There is an element of Desperate Housewives about it," the producer says. "It's a world of apparent comfort and happiness. Everything seems hunky-dory. And yet all sorts of secrets and lies are going on underneath the cosy suburban surface."

Hawes blames her character's egotism for the fact that this nice, middle-class world implodes. "Jen is clearly a woman on the verge of a nervous breakdown – she's having a mid-life crisis, or at least a thirties crisis. She's been seeing a therapist who's told her to stop harbouring this secret and get the truth out there."

All the same, the actress believes that Jen's behaviour will strike a chord with viewers. "I think people will recognise themselves in Jen. For her it's all about me, me, me, and we're all a bit like that. We're all pretty selfish most of the time, aren't we?"

For Hawes, the worst part of making Mutual Friends was filming numerous sex scenes. "Martin has visions of Jen and Carl making love all over town," she says. "The affair was actually only a couple of brief encounters in a car park, but in Martin's imagination, it gets wilder and wilder. It's quite Ally McBeal-esque. His brain wanders off in all sorts of different directions. Alistair had to come in on a Sunday and film all these different sex sequences. On the call-sheet, it had lots of variations on 'They're at it all over the place'. Poor him and poor me." She smiles mischievously. "On the Sabbath, too!"

The other strong theme running through Mutual Friends is male friendship. "It's rare that a TV series has a male friendship at its heart," Bullock muses. "There's an element of The Odd Couple to the relationship between Martin and Patrick. Martin is the Jack Lemmon type, uptight and repressed, while Patrick is the Walter Matthau figure, extrovert and responsibility-free.

"The drama is also like Sideways in that these two men are chalk and cheese. But there again, men do have the most unlikely friendships. We meet these boys at school and just cling on to them for no apparent reason. The problem is, we mature at different rates. Martin has grown up, and Patrick very definitely has not. Martin is the ego, fretting about everything, while Patrick is the id, joyously impulsive.

"One of the recurring themes is that Patrick is always getting Martin into trouble," he says. "At the same time, Patrick is Martin's salvation because he needs to loosen up. Every man should have a Patrick in their life to take him out from time to time, get him drunk and tell him to stop worrying. Jen and Patrick are in this tug of war for Martin's soul. In a way, this drama is a love triangle not between Jen and Martin and Carl, but between Jen and Martin and Patrick.

"Everyone will find Patrick really irritating," Armstrong grins, "but they'll also love him in the way they love Jeremy Clarkson. Patrick is brazen, splendidly self-deluded, has a terrible sense of occasion and really doesn't get it at all. He also serves the purpose of making everyone else look really responsible.

"All the same, there is something very refreshing about someone who doesn't take any nonsense from anyone. However childish and petulant Patrick is, there is something very appealing about someone who simply cuts to the chase. The innocent child in everyone will be jealous of Patrick."

"Comedy drama is a very tricky thing to get right," Bullock says. "You want to tell stories that have both substance and humour. Anil and Richard are able to write about raw human experiences and that all-consuming unhappiness that can descend when the optimism of youth evaporates and you think, 'Is that it?' But they can make that amusing without compromising the reality of it. It's a sunny, aspirational world – except when it's raining!"

'Mutual Friends' starts next Tuesday at 9pm on BBC1