It often appears that the life of a Wag is little but crystal-stud-ded mobile phones and Bottega Veneta handbags; yet to many, the most lingering image of Sheryl Gascoigne – surely the trail-blazer for the Cheryl Coles, Coleen Rooneys and Alex Currans of today – is of her sitting disconsolately at Scotland’s luxurious Gleneagles hotel nursing a black eye and dislocated fingers after her husband Paul’s infamous drunken attack on her in 1996.

The ink was barely dry on the glossy coverage in Hello! of their gloriously OTT wedding that summer, for which the magazine paid £150,000. As they posed for the official snaps – Gazza in gold brocade and his new wife in an eye-popping low-cut dress – it seemed that Sheryl truly was a girl with everything to celebrate. The struggling single mother from Hertford-shire had bagged the most compelling, mercurial sportsman of his generation: Gascoigne, who won 57 caps for England, was adored for his passion on the pitch (remember those tears during the 1990 World Cup?) and his endearing tomfoolery off it.

But the Gleneagles incident pointed to a disturbing reality behind the genial clown everyone knew as Gazza. Everyone except Sheryl. “I never called Paul ‘Gazza’, never,” she says. “Gazza was always someone else to me. This is part of the problem with Paul. People want him to be ‘Gazza’. They want to think, ‘Oh, what a shame, he’s such a hero.’ But the truth is there are some dark, nasty sides to Paul.”

The pictures loosened the first stitch in Gazza’s reputation – and showed the seemingly enchanted life of a footballer for what it really was: a gravy train of wild excesses and horrible comedowns. Even last week it was a subject of scrutiny once more, with Steven Gerrard, the Liverpool captain, charged with assault and affray after a man was attacked in a club.

But Gazza has always been in a league of his own. In the past decade he has degenerated into an alcoholic who has thrown away every opportunity, whether playing in China or managing lowly Kettering Town, through looking for life’s answers in the bottom of a glass.

What happened in Scotland was just one of many beatings Sheryl, 43, endured. By the time of their wedding he had been hitting her for four years, then weeping and begging for forgiveness and blaming his insecurity and the fear that she would run off with another man. According to her, she was naive enough to believe that if she married him, the violence would stop. It didn’t and, two years later, they divorced.

Yet the story of Gazza and Sheryl isn’t over. Spurred on by her children – Bianca, 22, and Mason, 19, who were adopted by Gascoigne – but opposed by Regan, 12, the footballer’s son, she spent last summer in a last attempt to save her former husband from alcoholic oblivion. Friends, she admits, thought she was mad. So why – especially after 10 years apart – would she put herself through it? Money? Fame? Helpless co-dependency?

“He’s my children’s father,” she sighs. “If it’s not my responsibility to help him, whose is it?”

We are sitting on a huge scarlet sofa in her newly refurbished home in a private road in Hemel Hemp-stead. Regan is wandering to and fro with Crystal, the family dog. A talkative boy who attends a stage school, loves singing and dancing and “hates” football, he seems to have gone out of his way to reject everything his famous father stands for. “Everyone thinks he’s Gazza but because he’s the top player doesn’t mean he’s a good dad or good person to be with, does it really? I don’t think there’s any point in helping him,” he says.

Gascoigne had already agreed to let a Channel 4 film crew follow him through the last stages of his treatment at the Priory clinic and out into “normal” life when Sheryl offered to let him move into the family home as he readjusted last summer. She had previously been approached to make a film about him herself and had refused, but was persuaded to take part this time by Bianca and Mason, who – unlike their younger brother – still have some memory of Gascoigne before the drink took hold and believe he can be saved. Surviving Gazza will be shown tomorrow night on Channel 4 at 10pm.

“As far as they were concerned, if Paul wanted to do it, they wanted to do it,” she says. “I’m one of these sad single parents who let the children have too much say – I know I am – but they are my life. I know some people will think it’s wrong but maybe we all needed to have one last go at seeing if we could help him.”

Besides, Sheryl has never quite shaken free of her former husband. Some have suggested she has Stock-holm syndrome – that she is the victim who has come to sympathise with her abuser. She insists her inability to let go is because Gascoigne was “the love of my life. I keep thinking I can sort him out and he keeps proving me wrong”. Still, laying open something so private can’t have been easy – especially in this manner.

Ever since the Wilkins family in the 1970s these kind of fly-on-the-wall documentaries have often proved painfully revealing. “It’s a stupid thing to do, really,” she says. “All I hope is that it will help some family in the same situation. I want to show to people who say, ‘Oh, he just needs a mate,’ friends’ husbands who say, ‘Let me know when he’s there, I’ll come and have a chat.’ They think they can just take him down the pub, sort him out. But it’s not as simple as everyone thinks.”

Or, more simply, she wants her share of the limelight – certainly in Gazza’s view. Last week (apparently forgetting it was he who had instigated the making of Channel 4’s film) he launched an attack on her, saying: “I can’t believe Sheryl has let our son be used on television. How can a 12-year-old understand the things I’ve gone through? Sheryl has turned his mind against me. If she hates me that much why is she still called Gas-coigne? Because the name Gascoigne is a bonus for her, that’s why.”

But she claims the lower media profile she has enjoyed over the past few years has been a relief. Her daughter Bianca, a surgically enhanced glamour model who won Love Island, a TV reality show, two years ago, has milked the Gascoigne name for all she is worth and though her mother says she supports her – “Bianca chooses to do what she does, that’s up to her” – one detects a flicker of disapproval in her eyes.

“I always hated being in the papers,” she says. “People criticising your hair or your clothes . . . And even when I was a footballer’s wife it wasn’t what you’d call glamorous anyway. Paul wouldn’t socialise. My friends say, ‘He kept you in a box so he could pull you out when he wanted you.’ A lot of footballers are old-fashioned, possessive.”

She says she gets no help, “neither emotional nor financial”, from Gascoigne, who is hopeless with money. She put her divorce settlement – “£600,000, not the millions people think it was” – into property. She doubled her investment and has paid her bills by buying houses and doing them up ever since. The house where we meet was also meant to be refurbished and quickly put back on the market, a plan that has been stalled by the credit crunch.

There is no denying that Channel 4 came knocking at the right time, and a residual part of her also longs to achieve something in her own right. She regrets having never had a proper job and looks in wonder at the likes of Coleen Rooney, who has built up a career to rival her husband’s. “Paul’s attitude was, there’s no way my wife’s going to be working. When breakfast TV started I got an offer but he just said, ‘What would you want to do that for?’ ” Still, it was a gilded cage, at least at first. The couple met when Gascoigne, who was then playing for Tottenham Hotspur, became a neighbour of Sheryl’s in Hertford. Having split with her first husband, she was alone with two small children and dazzled by his attention.

“He was a drinker, like lots of footballers are. It never occurred to me that it was a big problem, and he was charming, he swept me off my feet. He was brilliant with the children, especially Mason, who was only 18 months old . . . He’s the only dad they’ve ever known.”

In the event, Gascoigne lasted just 12 days at home before going Awol, leaving the Channel 4 film crew behind. What they were left with were Sheryl and the children’s attempts to find him: a moving portrait of the impact that alcoholism has on a family. It also provides another clue as to why Sheryl has found it so difficult to let go. Gascoigne is obviously a profoundly sick man, shambling around the house with his dressing gown hanging open, suffering bouts of suicidal depression and paranoia.

The family are by turns conflicted and distraught, but with the help of a therapist they begin to see that by keeping the door open, they have simply become part of his problem and now have to let go. Sheryl’s had no contact with Gascoigne for three months now, and won’t – not unless he’s checked into rehab and stayed there for at least a month, of his own accord.

It’s easy to say, of course, harder to do. If her mobile rings and it’s him needing help she swears she won’t answer – but I wonder.

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