When my wife Kate touches the side of her jaw, it’s because it aches. If she stands in a certain way, her sciatica is playing up. These days I notice these tiny inferences that she’s feeling under par.

I listen when she talks, making eye contact, whereas once I would have hidden behind my newspaper grunting intermittently, feigning interest.

Today, I can say that our marriage is robust and joyful: full of laughter, occasional healthy bouts of contention, and above all, love. And the reason is that I’m in tune with Kate. I’ve learned to put her first; to think about her and what she needs. That’s hard to do all the time, but I’m getting better at it.

When my wife Kate touches the side of her jaw, it’s because it aches. If she stands in a certain way, her sciatica is playing up, writes Harry Benson (File photo)

I’ve learned from my own bitter experience that a marriage can unravel when a husband ceases to care enough about his wife. In fact, most marriages don’t end with rows, adultery or even incompatibility, but with an aimless drift into separation.

‘Growing apart’ has now officially overtaken infidelity as the main cause of family breakdown in Britain, and the tragedy is that it is often utterly avoidable.

Relationships that could be salvaged — that are just going through normal, unhappy phases — are needlessly in jeopardy as couples sleepwalk into divorce. We’ve reached crisis point. Nearly half of teenagers sitting their GCSEs this year are not living with both natural parents.

Yet there is hope. It may sound counterintuitive, but the evidence is that staying together in an unhappy marriage — and I’m not for one second talking about the tiny minority of awful or abusive ones — could be the best thing a couple ever do.

This seems an astonishing proposition until we recognise that unhappiness is often a transient state.

Bad situations improve. Children grow up and become easier to manage. People change their attitudes.

Intent is the over-riding factor: if we want to stick together — for better, for worse, in sickness and in health — then we will.

I’ve spent the past 20 years teaching thousands of couples how to have a happy marriage and am now research director for Marriage Foundation.

And my formula for fixing things is a simple one: ‘Happy wife, happy life’ is a maxim that is backed by research and has saved my own marriage.

First-hand experience and a survey of almost 300 mothers my wife Kate and I carried out for our latest book, What Mums Want (And Dads Need to Know), corroborates this. Half the mothers we questioned who were now ‘happy with their relationship’ had at some point in the past been ‘unhappy’. One-quarter had been ‘very unhappy’.

And the mums we surveyed told us that friendship, being ‘interested in me’ and ‘interested in the children’, and ‘being kind’ are the key qualities they seek in their spouse.

Surprisingly, at the bottom of the list come ‘fixing things’, ‘earning a decent wage’ and ‘being adventurous, strong and sexy’.

What’s more, when Mum is happy, the rest of the family tend to be happy. This is much less true for dads. It is a simple truth that I have now acknowledged.

When I take responsibility for our marriage, and put Kate first in my pecking order of priorities, the rest will follow.

I learned this through first-hand experience when our relationship reached a crisis point. It happened eight years into our marriage when Kate told me she was profoundly unhappy.

I learned this through first-hand experience when our relationship reached a crisis point. Pictured, Harry Benson

‘You know I love you, Harry,’ she said. ‘But since we’ve had the children, I’ve found it harder and harder to talk to you. We have a comfortable life and you’re wonderful with the children when it suits you. But you don’t seem at all interested in me. We don’t seem to be friends any more. I feel lonely and unimportant. I’m not sure how long I can go on like this.’

The white flash that shot through my head like a thunderbolt temporarily blinded me with a mixture of panic and terror. Was my marriage over? I never saw it coming.

Looking back, I can’t believe I could have been so oblivious to the fact that we were so perilously close to collapsing. We’d rarely rowed. We had two young daughters we both adored and my job as a stockbroker in Hong Kong gave us a comfortable lifestyle. My immediate fear was that I’d lose my children. Losing Kate would mean losing them. The thought shocked me to the core.

Everyone accepts that good marriages can go bad. But it was never going to happen to us, was it? Yet insidiously we’d grown apart and, without knowing it, were drifting toward a break-up.

Fortunately for us both, Kate didn’t leave me. As a result of the decision I made to put her first, to be her friend and take notice of her, we not only stayed together, but after 30 years of marriage — I’m now 56 and Kate is 52 — I can honestly say that today we’re both happier than we’ve ever been.

Had I known then what I know now, we would never have got into the mess we did. Kate was a natural mum so it was easy for me to take a back seat at home.

I now know that my prime role is to take responsibility for my marriage, to love Kate, to be her friend, to be kind. When I do that, our marriage stays strong, we parent well as a team, and family life works well.

That’s what mums want. That’s what dads need to know. After Kate’s ultimatum 22 years ago, we went, reluctantly on my part I admit, on a marriage course.

On every level since, our lives have undergone a sea change. We moved back to Britain in 1997, went on to have four more children — our brood of six comprises Rosie, 25, Polly, 23, Gracie, 19, Sizzle (Cicely), 17, Charlie, 15, and 13-year-old Johnnie.

I learned to stop taking Kate for granted. I started to show her affection, to say, ‘I love you’; to notice the new dress she was wearing and to ask how she was feeling. I learnt to be kind to her — and this meant sometimes not doing the things I wanted to do.

And this week, the first in January after the New Year holidays, when lawyers are inundated with couples seeking divorces, I’d advise all of them to pause before they take an irrevocable step.

In conjunction with Professor Stephen McKay of the University of Lincoln, we analysed data from a large national survey of mothers. Most of the mums who were ‘unhappy’ with their relationship when their babies were born now said they were ‘happy’.

More amazingly, half of the mums who had been unhappiest now rated themselves ‘very happy’ with their partners a decade later.

The biggest worry is the tendency for couples who are reasonably happy to drift into separation.

In a study I did for Marriage Foundation, this time with Professor Spencer James of Brigham Young University, Utah, we found that two out of three couples who separated had reported one year earlier that they were happy.

Like Kate, most women want friendship more than anything from their husbands. That’s it. It’s not about being a doormat. I learned to really love Kate and she loved me back. That’s what mums want. And that’s what dads need to know. It’s a disarmingly simple formula, but it is the key to a happy and enduring marriage.