Pattie Boyd, former wife of George Harrison and Eric Clapton, married for the third time at Kensington and Chelsea Register Office recently. So far, so rock’n’roll. But Boyd, 71, has been living with Rod Weston, 62, for the best part of 25 years.

“It’s almost our silver anniversary so we thought we had better get on with it,” said Weston — which didn’t answer the questions “Why? What’s the point of getting married after all this time?”

Boyd and Weston are not the only ones. Late late marriage, to the person with whom you have already spent the best years of your life, is shaping up to be this spring’s hottest trend.

Alan Rickman recently married his partner of 50 years; Jonathan Pryce has just tied the knot with Kate Fahy after 43 years; and just recently, Bob Geldof married his girlfriend of 19 years, Jeanne Marine.

Weird, no? Why this sudden crazy rush to call each other man and wife when they’ve already proved they’re a winning team? Cynics might suspect it has something to do with avoiding inheritance tax; pre-election housekeeping.

But it doesn’t entirely explain why Pattie and Rod dressed up in their best bib and tucker and posed for photos joyfully, or why Bob Geldof gathered all his children for their South of France ceremony. These were weddings like all weddings — a declaration of love and commitment, the rubber-stamping of a partnership that you hope will sustain you until death.

The big difference, of course, is that for these couples, death is no longer a remote possibility. With hindsight, and their twilight years looming, they have come to see this is as good as it gets. I say “they”, but I mean, of course, the men.

What we are witnessing here is a classic case of late-onset gratitude, with a small side dish of guilt. (Men and women can both experience this emotion but it’s more prevalent in men).

In your sixties, all the “what if?”s melt away, and any niggling suspicion that you could have had the life of the Beckhams if only you had picked someone more organised is a distant memory. You have grown up and feel lucky, blessed (if you can bear that word) to have what you have, as opposed to mildly aggrieved that you are not able to have it all. Your midlife crisis is passed. Your health scare has shaken you up and you want to make amends.

Behind every late marriage is a man who has woken up one day and thought: “Ah. I definitely owe her. I owe her big time, and I’m not sure a handbag is going to do the job this time.”

The challenge, then, is how to show your appreciation, after receiving several decades of wifely service and, unfashionable though it may be to admit it, there is no way of saying, “Thank you — I love you” as effectively as a marriage proposal, whether you are a believer in the institution or not.

If the recipient is not in the first flush of youth, it is doubly effective. As someone who got married lateish — in my forties — I can confirm it is nice to be asked at a point in your life when you are officially no longer viable marriage material.

I am not suggesting every unmarried woman in a long-term relationship is secretly praying her partner will pop the question — I know at least three who would rather stick pins in their eyes than call themselves a wife — but there is something especially romantic about an older man choosing to publicly celebrate his love of an older woman.

That’s another advantage to getting hitched late in the day: you get to feel that you are embarking on something slightly superior to a regular marriage. Pledging your troth when bits are falling off you is, in many ways, braver than getting hitched in your twenties or thirties.

These people are saying: “I’d rather be wheeling you around with an oxygen tank than clubbing in Ibiza with a younger version”, and there is something almost noble about that.

Marrying at a time when the bedroom has become the place where you go to put in your earplugs, pop a Rennie and slip on your anti-snore equipment — that’s proper, grown-up, selfless love. Of course, 64-ish (as Paul McCartney anticipated) is when a man starts to feel vulnerable and realises his priority is being needed and fed, and dandling grandchildren on his knee.

Unless you’re Mick Jagger, your sixties is when you find you can’t get your socks on without assistance and you need someone to help you reverse the car on account of your cricked neck. You probably can’t hear so well at parties, your stamina isn’t what it was, and you certainly can’t attract the opposite sex.

What once seemed a conservative, limiting and deeply uncool choice starts to look like a sensible security measure. Marriage doesn’t guarantee there will be someone there for better or worse, but you might as well try to lock in your potential carer now.

But I have another theory as to why late marriage is taking off. There just aren’t enough parties once you get past 50. The only time you see old friends gathered together en masse is at funerals. One big advantage of a late-in-the-day wedding is that you can have a knees-up with all the people you most care about without. It can be small and personal, you get to wear what you like, bouquet and bridesmaids optional.

And, last but not least, it’s the perfect opportunity for fulsome speeches about how fabulous you are: your own personal Lifetime Achievement Award and eulogy rolled into one. You can see why it’s catching on.

Who knows? Maybe even Kurt Russell and Goldie Hawn — a couple for more than three decades — will tie the knot one day.

— The Telegraph Group Limited, London 2015