Belinda learned the hard way that along with canvassing and party conference, the tabloid exposé is an occupational hazard for politicians' wives. But she found it in her heart to give her hubby a second chance.
"It is possible to forgive if you are able to sit down and look at the bigger picture," says Christine Northam, a senior counsellor with Relate, the largest relationship and sex therapy provider in the UK.
"People have affairs because something is wrong with their intimate relationship but they cannot see it. It is a symptom of deeper problems. If couples can get their heads around this and look at the context of the affair, it is far easier to forgive and move on," she says.
Adultery may be the ultimate betrayal in a relationship, but it is just one of a string of modern-day scenarios in which individuals are faced with a choice between forgiveness and castigation. Business partners, band members, siblings, parents, best friends, political allies and even nations are all prone to falling out on a regular basis. Few are immune to the pains of a split with a former friend, ally or lover.
"Historically, women were more inclined to forgiveness because of their position in society," says Professor Stephen Palmer, director of the coaching psychology unit at City University in London. "But the demographics have changed and independent women today are more able than ever before to choose not to forgive someone."
The concept of forgiveness may appear all the more alien at a time when professional, family and social pressures conspire to make the average existence a whirlwind of stressful demands with little time for those who get in the way or are a cause of friction in life. This is manifested in restaurant rage, road rage, shop rage - and if we can't forgive someone whose trolley gets in our way, what chance is there for the friend who starts dating your old boyfriend or talks behind your back?
But not being able to forgive is likely to make you feel even worse, according to Professor Palmer. "If people accept and forgive, it is much healthier than remaining angry," he says. "Staying wound up over something and letting it eat away at you is likely to prolong the symptoms of traumatised stress. The influencing factors that enable a person to forgive are role models as a child, your religion, your cultural beliefs and, most importantly, your willingness to be pragmatic and move on."
But some find it harder to forgive than others. The Sultan of Brunei and his brother Prince Jefri have been locked in a bitter fraternal feud for nearly a decade. Things brightened briefly this month when the sultan dropped embezzlement charges against his brother, but the pair have still not spoken in two years. And Jude Law had no qualms about pleading for forgiveness from his fiancée Sienna Miller, following his affair with his children's nanny. But when Miller in turn indulged in a fling with his friend Daniel Craig, it was not so easy for Law to forgive.
"I think it's difficult to forgive somebody if that betrayal impinges within the very core of your belief," says Professor Windy Dryden, professor of psychotherapeutic studies at Goldsmiths, University of London. "When a person's sense of identity is fundamentally challenged, that person might not be able to forgive. The cost will be too high."
One person who earlier this month displayed the most extraordinary ability to forgive is Sarah Carew. Her partner was given a four-month suspended sentence for attacking her by biting her ear while she was eight weeks pregnant. Yet Carew happily announced that she had forgiven the aggressive antics of her partner and welcomed him back into her life.
"Being able to forgive is all about your attitude," says Professor Dryden. "There are obviously complex factors such as the extent of the betrayal and whether that person wants to make amends. But one main issue is having an inner philosophy that enables forgiveness."
And at the more extreme end of the spectrum are the serial forgivers who are always willing to give someone another chance - with traditionally dubious consequences.
Doyenne of the art of forgiveness is the violet-eyed temptress Elizabeth Taylor. It was with considerable panache that she divorced her husband of 10 years Richard Burton in 1974 - only to remarry him in a lavish ceremony 16 months later. But her attempts to forgive and make amends with her fifth husband were to prove doomed and they separated for good the following year amid reports of Burton's heavy drinking.
The key to success is to remember that forgiving and forgetting are not the same, the experts say. "There are boundaries in relation to what people are prepared to put up with in terms of forgetting and getting over something," says Professor Dryden. "But this is not necessarily the case in terms of forgiveness. You can forgive someone but not necessarily forget."
And so some can forgive and move on, others simply can't. Only time will tell if Belinda and philandering Mark manage to survive his betrayal and save their 13-year marriage.
There is a possibility that they will defy the cynics and salvage their relationship with a bout of mutual forgiveness and a healthy dose of counselling. But if not, Belinda may do well to consider a job change and abandon the troublesome role of politician's wife altogether.
After The Affairs: We are happier today than we have ever been before
Gary Hemmings, 53, an oil and gas industry consultant, lives with his wife Sylvia, 51, an accountant, in Norwich. They have two daughters aged 26 and 24
SHE SAYS: I had three affairs when my husband was working overseas. I hated all the deception but there was clearly something missing from my life. I confessed to him and was very relieved when he decided to stay with me. But it was clear he couldn't forgive me. It was a very unhappy time. We papered over our problems. Our marriage may have looked respectable but it was a nightmare. It still came as big shock when he told me he was having an affair and left. I suppose part of it was revenge. But it still hurt. We had two children and it was extremely difficult. When he eventually came back to me we both realised we had to forgive one another if we were ever going to move on. We had a lot of counselling and our relationship became completely different. We realised that forgiveness is a choice. When you forgive and work through things, it brings you closer together than ever.
HE SAYS: I was completely shocked when Sylvia told me about the affairs. I thought our marriage was fine. The bottom of my world fell out. It was devastating. I didn't want to give up on the marriage but it was difficult. I could not forgive her for what she had done. I really struggled to move on. We didn't get any help in terms of counselling so the issue was left to fester. Things came to a head when I had an affair with an old girlfriend and I left my wife. But again it was a real struggle, this time with my conscience. I felt terrible about what I'd now done. I eventually went back to Sylvia and we started again. We had to rebuild our lives from scratch. But by forgiving one another, we were released. Today, we are happier than we have ever been. I wouldn't wish what we went through on my worst enemy. But I'm glad it happened to us because we now have a relationship that is incredibly strong.
SARAH FERGUSON AND THE DUKE OF YORK Unflattering images of a topless Sarah Ferguson having her toes sucked by her business adviser appeared in the tabloids in 1992.By 1996, the couple were divorced. They stayed friends and lived in the same house with their children for years.
EMINEM AND KIM MATHERS When Eminem spotted his wife, Kim Mathers, kissing another man in a Detroit bar six years ago,he pistol-whipped his love rival. Then he wrote a song about wanting to murder her. But love works in mysterious ways. They were recently reconciled and married again this month.
KIMBERLY AND STEPHEN QUINN When it was revealed in 2004 that her older son had been fathered by David Blunkett, Kimberly's husband, Stephen, was very supportive. "Kimberly and I discussed everything," he said. "We said, 'Should we remain married?' and both of us said passionately, 'We want to do this; we will do it'."
BRETT ANDERSON AND BERNARD BUTLER The relationship between the founder members of pre-Britpop chart-toppers Suede imploded in 1994 in a haze of rock clichés, including drug abuse, bruised egos and, oh yes, "musical differences". Their reunion as Tears in 2005 was disappointing musically, but at least they were friends again.
PAMELA ANDERSON AND TOMMY LEE She was famous for her pneumatic physique and ability to run in slow motion in a red swimsuit. He was a tattoo-covered heavy-metal drummer. They married in 1995 and divorced in 1998, after Lee admitted assaulting her. But they made it up the following year, then parted again.
WAYNE ROONEY AND COLEEN MCLOUGHLIN When Coleen found in 2004 that her fiancé had "romped" with prostitutes including a grandmother known as the "auld slapper", she was so angry she threw her engagement ring into a squirrel sanctuary. She has since found it in her heart to forgive the millionaire football star.
BILL AND HILLARY CLINTON When Bill embarked on an affair with intern Monica Lewinsky, it sparked global media interest and led to his impeachment trial in 1999. Hillary won sympathy playing the role of the dignified but wronged wife, before taking him back. Bill Clinton's popularity soared, Hillary's career took off.
GORDON AND TONY At Granita restaurant, Islington, in 1994, Gordon agreed not to stand for the Labour leadership. In return, said Tony, he could take over the top job. When Gordon ran out of patience, he became petulant and bitched about Tony behind his back. Now all is forgiven. Gordon has even been spotted beaming at Tony.
NORMAN COOK AND ZOE BALL They had it all: marital harmony, an adored son and the perfect Hove home. So it came as a surprise when in 2003, four years after they wed, Ball had an affair with London DJ Dan Peppe. Weeks of media speculation ensued. Eventually Ball revealed her husband had forgiven her. So far, so good.
HARRY REDKNAPP AND PORTSMOUTH FC When Harry resigned as manager of Portsmouth in 2004 to "take a break" from football, then joined arch-rivals Southampton two weeks later, fans were incensed. But a year later they didn't seem to mind that "Judas" had been given his old job back by chairman, Milan Mandaric, left.
Additional reporting by Katy Guest and Keith Laidlaw