It could be a provincial Pizza Express: a huge hall filled with little tables for two, each laid for dinner with napkins, cutlery and a gerbera in a vase. But the couples wandering to their tables with heaped plates of pasta and plastic cups of orange juice seem strangely young and glamorous. Many are in their twenties; the women have diamonds twinkling on engagement fingers, immaculate blonde-streaked hair and a uniform of pale beige cashmere.

They are here for session four of the Marriage Preparation Course at the Holy Trinity Brompton, London’s trendiest Anglican church; and, although it’s a damp Monday night, the place is absolutely packed. It’s a sight that would warm the heart of any politician – because when it comes to policy-making, marriage is à la mode. In recent weeks, both Labour and the Conservatives have been pledging tax incentives to encourage people to stay married, in response to unequivocal statistics showing the health, educational and social advantages bestowed on the children of married couples. They are certainly onto something. A survey by Radio 4’s Woman’s Hour found that the majority of people believed it was a good idea to settle down before 30, and that almost 40% thought children were best looked after by a stay-at-home mother.

“Theoretically, it’s extraordinary that people still bother to get married – myself included,” says Francesca Beauman, 30, author of The Women’s Book, a zeitgeisty guide for her generation. “A fair number of my friends have chosen to take the ‘have a baby, then get married’ route, rather than the other way round; but the fact that they go through with the ‘get married’ bit is interesting. After all, our mums’ generation fought for the right not to. We are all far more conventional than we like to believe, no doubt in reaction to our parents.”

Even today’s Carrie Bradshaws still hanker after a trip up the aisle with Mr Big, it seems. And more of them are prepared to work at it: divorce has dropped to its lowest level for two decades. And, in spite of the persistent divorce culture, women still aspire to marriage.

“I feel cautious about it,” says Emily Strawson, 31, a trainee GP whose parents split in a divorce she describes as traumatic. “But I still want to do it. For me, getting married is a romantic gesture. There’s a formality that appeals to me. I want to be in the generation that has successful marriages.” She says that witnessing what her parents went through has made her more determined not to follow in their footsteps.

Certainly, disposable marriages seem to be over. Zoe Kirby, 29, was left by her husband, Richard, nine months after the birth of their daughter, Sophie. They sold the marital home and moved into flats near each other. “I discovered how strong I was,” she says. “Because I had a baby, I had to keep going, and I knew how sensitive babies are to their mother’s emotional state, so I made sure I was always positive.” But, far from resenting her husband’s behaviour, or going all-out to find someone else, she persuaded him to attend the Holy Trinity’s Marriage Course with her. They are now back together and, she says, happier than ever. “Mentally, I never gave up on the marriage.”

According to Penny Mansfield, director of One Plus One, a charity devoted to marriage and partnership research, one reason that the divorce rate is dropping may be a change in our values.

“Maybe it’s global warming, but younger people are taking the view that the important thing is to make the best of what you’ve got, and that it’s good to repair things and hang onto them, rather than buying something new,” she says. “Maybe it is an attitudinal shift that will be more prevalent among young people when it comes to relationships.”

If marrying rather than living together becomes a fashionable lifestyle choice, we may well see the numbers of couples tying the knot rising again. “I wouldn’t be surprised to see marriage becoming attractive again,” Mansfield says. “I’ve got daughters of my own, and I can see that they think it would be a good thing to do.”

It’s a different story for their parents, however. “From my experience, the biggest increase in divorce in the past year has been among 50-year-olds,” says the divorce lawyer Vanessa Lloyd Platt. “Partly, it’s when the children leave home. But also, women have more money and a sense of freedom, and they’re going mad out there. The trouble is, we’re living too long. People weren’t built to have relationships that last for 50 years.”

When Jonathan Robinson, a retired university lecturer, turned 60, separation from his wife seemed the best solution to a difficult situation. “There was warfare at home,” he says. “Things got to the point where I couldn’t take what was being asked of me. We were going to go to Relate, but I thought, I don’t want to sit down and go through all this stuff.”

He has had to move from the home counties to rural France because he is unable to support two homes on a pension, and worries that he is losing touch with his grown-up children because he lives so far away. “A lot of people in this area of France are on their own,” he says. “There’s a sense of desperation about them, all trying to find a new partner in their old age. It’s horrible to go back to the dating scene in your sixties.”

As Beauman says: “I think the continuing enthusiasm for marriage exposes a powerful streak of optimism that exists in the human spirit. It’s the voice in one’s head that continues to squeak, ‘My marriage will be the one that works – oh yes it will’, despite all the statistics suggesting otherwise. In fact, I often think that self-delusion is vastly underrated. It makes the world a much happier place.”

YOUNG AND MARRIED: Ruby Warrington, 31

I was the first of my friends to get hitched, at the age of 27. I liked being the first – it felt quite rebellious. I proposed to him, but my friends had advised against it – they thought I was being swept along by the romance. But we’re still together after 10 years.

I’m pleased not to be in that thirtysomething singleton scene – the pool is getting smaller and smaller. I sense people my age feel there is something missing if they haven’t found someone.

Getting married never meant being tied down; we haven’t decided if we will have children yet. Being committed has allowed us to be more free in our separate social lives. Lots of people say, “God, you so don’t act married.” There is a lot of stigma attached to marriage – people think of it as fusty, as though all I do is sit at home darning his socks. Yes, we have a mortgage, but we still have fun together.

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