For Richard Haig, 57, from Tunbridge Wells, who divorced six years ago, it was a drive to be happy and a belief that a better relationship must be out there.
"After we had our two children, my wife became a stay-at-home mum and we just lost the connection," says Haig, who runs his own technology business. "I felt the children were my ex's priority and everything was about them. We rarely got babysitters, she didn't want to go away as a couple and all the conversation revolved around the kids. When I married, I wanted to share my life with someone, not share my children's life with someone."
Haig travelled to Asia for business and started having affairs. "It started off as a sexual thing because the physical side of my relationship with my wife had died out, but it soon became a search for something deeper. I was looking for someone to connect and fall in love with."
When the affairs came to light after 18 years of marriage, they agreed to start therapy, but Haig went into it half-heartedly and after a few sessions initiated the divorce.
"Even though I was in my early 50s, I felt like I was young enough to get back out there and I didn't want to miss my chance at being happy again," he says. "I lost everything: the two holidays a year, my beautiful home, my warm family environment surrounded by my children. Suddenly, I was alone, tortured with guilt, in a rented flat, having to do everything for myself and not knowing when I was going to see my children next."
So would he do it again if he had his time over? "Definitely," he says. "I'm now in a fulfilling relationship and I'm so much happier. I think I'm a better father, too."
Andrew Marshall, marital therapist and author of It's Not a Midlife Crisis, It's an Opportunity, believes today's shift towards "over-parenting" is a huge contributing factor.
"Today's society says children have to come first and we worship them far too much," he says. "While it might be okay when the children are younger, when they leave home, empty-nesting parents end up looking at each other and feeling they have nothing in common. Add the world of social media and internet dating, and the fact we're living longer, men will often give up on their marriages, even in midlife, thinking they have time to find happiness elsewhere."
Family Law in Partnership, a London law firm, reinforces this theory, having seen a jump in the number of male clients seeking a divorce. It has set up divorcediaries.co.uk, featuring the voices of men sharing their experiences to help others.
Chris Rogers, 45, a doctor from Maidstone, Kent, talks of wanting to be truly honest with himself and to pass on that message to his two children, even though they were hurt by their parents' split.
"I grew up in a household where there was seemingly no conflict and yet my parents split up out of the blue when I was 18," he says. "It made me feel they were living a lie and I didn't want that for my kids. I wanted them to know how important it was to be happy and honest."
But men aren't just filing for divorce because they are disgruntled. According to the psychoanalyst and writer Esther Perel in her new book, State of Affairs: Rethinking Infidelity, the rate of married women who report they've been unfaithful has increased by 40 per cent, while the rate among men has stayed the same.
Infidelity, says Gurpreet Singh, a Relate counsellor, can be a hurdle too high for any marriage to overcome. "In Relate's research, one in 10 divorcees said with the right support they would have been able to save their relationship. But we know that men are less likely to access support when there are problems such as infidelity and this may ultimately make divorce more likely."
Jane Tenquist, partner and head of family law at Myerson Solicitors, which services Cheshire, has certainly seen an increase in the number of over-50s male clients bypassing therapy and seeking a divorce.
"They're healthier and living longer and there might be a trigger, like a loss of a parent, which makes them realise they don't want to remain in an unhappy marriage for another 20 years -- even if it's going to cost them financially."
Practically, men are starting to feel braver, too.
"There's more of an assumption that the courts will give them a fairer hearing these days as fathers and providers," says Tenquist. "For example, courts won't necessarily think that women should be 'kept' and are more likely to expect women to earn and provide for themselves, especially if there are no longer children at home. Courts are also more in favour of securing a proper father/child relationship because there is so much evidence that children do better with both parents, rather than just one."
Yet Michael Lewkowicz, who runs Families Need Fathers, believes men are erroneously hurtling towards divorce for precisely this reason - and finding that their treatment in court falls short of expectations.
"Men assume they will get a fairer deal because families are built so differently now with dads being more hands-on and women often being the breadwinners," he says. "But this greater equality between the sexes in real life is sadly not being matched by the courts and usually ends up in disillusionment and disappointment, with men losing out financially and with their children."
Indeed, in a survey commissioned by Yorkshire Building Society, men were shown to suffer more emotional trauma than women after a marital break-up and more than two years after a divorce, 41 per cent of men were still sad about the failure of their marriage. For women, the figure was 33 per cent.
This is why Marshall has a note of caution for men who think divorce may solve all their problems.
"It can be a myth that the grass is greener elsewhere and divorce will make things better. Instead of taking a wrecking ball to your life, it may be more helpful to examine your existential pain, understand why you're so unhappy and try to work with your partner to come towards a happier resolution."
