During their tempestuous nine-year courtship, my mother gave my father back his engagement ring which, with typical Yorkshire pragmatism, he sold and used the cash to buy a suit. They were reconciled but he never replaced the ring, so my mother didn’t get her diamond, although this week she did have her diamond wedding.

Sixty years with the same person — “Three life sentences” as my father drily put it — certainly merits the envelope from Buck House that arrived with absolute efficiency containing a lavish tasselled card bearing a comically grumpy photo of the Queen. Perhaps the last truly useful function of royalty is being a magical enough personage that even her (probably) laser-printed signature gives affirmation to our personal triumphs.

That card impressed the postman, made the large African lady in the party shop on the Walworth Road grab my surprised mother in a flamboyant hug, will no doubt be swanked around my ma’s hairdressers next week before being locked in a box of special stuff. Like most ordinary folk excluded from the circuit of gongs and titles, it amounts to the greatest official honour of their lives.

In a new report Every Family Matters, Iain Duncan Smith’s Tory think-tank has proposed lobbing the nation’s marrieds a £20-a-week tax break for not getting divorced. This sum might give a little quantitative easing to some domestic economies or provide couples with a weekly bonding Indian takeout/DVD combo. But I wonder if a better use of government funds might be to strike a new series of marriage medals. Using the odd and seemingly random traditional gift list — first year is paper, ten is tin, 40 ruby etc — the system would reward long service. You’d have to labour 25 summers in the marital salt mines before you got anything remotely decent: ie, silver. But a marriage medal would be a fair exchange for our contribution to social cohesion, a public affirmation and a charming collectible.

The reason marriage is so seldom politically celebrated is for fear of offending the divorced. But I am yet to meet a divorced person who did not believe lifelong marriage was a righteous intent or did not feel sadness that he or she was unable to achieve it. And there are few married people who do not appreciate how, but for some unforeseen misstep, they might end up locked in a legal death clinch. That even a good marriage can at times feel like running a three-legged race carrying a carping, sharp-clawed monkey provides some insight into the dark horrors of a bad one.

As a young local newspaper hack, I’d often be called upon to interview diamond wedding celebrants. And when asked the inevitable question about the secret of a long union, they’d answer, as if some edict had been received, “a bit of give and take”. Marriage in old age looked like a peaceful plateau to be relished after the brambly rock faces of midlife.

But what surprises me about my parents, and several other longstanding couples I know, is that they still have the most poisonous, huffy rows. “Give and take” was obviously code for “give him a roasting over his inability to Sky-Plus Countdown” and “take offence at the slightest black look”. But that my parents occasionally go off like firecrackers, and have been doing so throughout my life, means I entered my own marriage understanding that it wasn’t all spoilt by the first teary tiff, or even the 25th.

But maybe that is the point which is missed in the myth of perpetual romance — amid the ever more arcane dove-releasing modern weddings rituals — that marriage is gruellingly hard, something to be endured. It is no surprise that one in three ends in divorce; what is astonishing, magnificent, a feat of true endurance, is that two thirds still succeed. All that love overcoming the existential agony of having a never-changing five rows with the same person for all of eternity.

The point is, all this is worth enduring, because marriage feels like home. Although I often yearn for solitude, to do for once exactly as I please, I find when my husband goes away I’m unable to relax, to settle on a particular TV show or eat a proper meal. I am restless, slightly lost. The joint suicide of Sir Edward and Lady Downes this week will be understood by all long-married couples. For Sir Edward who, unlike his wife, was not terminally ill, this was no romantic gesture but a practical one. Love was all that made the indignities of age bearable. Without love, why bother to go on?

Losing your pole star, as Joan Bakewell put it, to navigate by, the landscape is bleak and meaningless. Many elderly couples — several in my own family — died within a few months of each other, even though the remaining spouse had been in fair health. They just released themselves to death, threw their bodies willingly on the pyre. A friend’s widowed mother, hitherto abstemious, every morning walks half a mile to the off-licence to buy a bottle of wine, which she consumes by the afternoon. Sometimes she goes back for a second. Without her beloved husband, life is only tolerable blurred.

In a final letter to her relatives, Lady Downes concludes: “I send love to you all and your extensive families. Enjoy it while it lasts.” It was the understanding achievable only at the end: if only we could truly compute that our lives are finite spans we’d eliminate half our anxieties.

One morning I was cycling along a beach, with my sons — who were very small — pulled in a contraption behind. It was a moment that should have been lovely: but the boys were squabbling, had woken me too early, the weather was turning to rain. And an old lady, all alone on the shingle, seeing my cross face, called out: “Enjoy it, dear, those are the best days . . .” And they are, and we should grasp them.

Of my parents’ 60 years, only 18 of them — a tiny proportion — were concerned with childraising. For the rest they were alone together. That ought to refocus the mind: in our fixation with being perfect parents, allowing our children to suck up all our leisure time, we often underrate the one relationship that will endure when everything else — career, children, health — is gone.

A week before their big anniversary, my father said to my mother: “Come on then, I’ll get you that diamond.” So they went off to some jewellers and, astounded by the prices, although they had a bit put by, decided not to bother. After all this time, it is enough of a gift that they have each other, that they can still keep buggering on.

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