The divorce rate is rising among the over 60s.

It’s dropping in other age groups. Silver separations are bucking the trend. It’s a growing phenomenon and people seem surprised. Not me. I never cease to be amazed that so many marriages survive a lifetime.

Think about it. Two strangers meet in their twenties. They hurtle towards one another and the altar – mainly thanks to sexual attraction. Then they set up house with a promise to live together for the rest of their lives.

Throughout their thirties, forties and fifties, the relationship is carried along by a joint commitment to children and mortgage repayments. A shared love of home and family strengthens the bond. Decades pass as the couple raises their brood; rushing off to work and coming home with provisions (much like the penguins in Frozen Planet).

Then, around the time the bus-pass arrives, the youngest child graduates or gets a job away from home. The nest is empty once more. The end of the parental task can coincide with retirement from work. The roles that have defined the husband and wife are gone. Twenty years of good health may remain.

They are returned pretty much to the state in which they met – minus the freshness, the mystery and probably the libido. When the six o clock news comes on, it’s just the two of them staring at the box. Two bowls laid out for porridge at breakfast; two plates for lunch and supper.

Do they eat in silence with nothing left to say to each other? Do these two people who chose one another most of their lifetime ago still make a couple?

I am one of those who believe that marriage is the foundation stone of society and the best environment in which to raise children. But life ended earlier when the rules were established. Now that we are fitter for so much longer do we need to negotiate a new post-marital phase?

Sixty is the perfect age to seek the answer.

Sixty was traditionally the portal for the end of the road at three score years and ten. Now it can be a platform from which to spring into a new phase of life.

Sixty used to mean grey hair and flat shoes. Today sixty- somethings include Twiggy, Lulu, Joanna Lumley and Helen Mirren. George Clooney is fast approaching it. Today people in their sixties are fit and active and often have the financial independence to continue to regard life as an adventure.

Sixty is an age of honesty and openness. It’s a time to tell it like it is – because there really won’t be another opportunity to do all the things that a lifetime of work and child-rearing have left undone.

It’s tempting to think the restlessness is also a modern phenomenon but I’m not so sure. I remember planning a trip across Europe when I was a student and my mother suggesting that she could tag along. She would have been about 60 and although her suggestion was made jokily, it always plucked at me that I didn’t include her. I think she too was longing to spread her wings.

Her generation didn’t have that choice. They were housewives whose pensions were adjuncts of their husband’s. Travel was more expensive and less accessible.

Women didn’t start their own businesses the way they do today. They didn’t go back to university as mature students. They do now. They return in droves. They didn’t then have the opportunity to continue to explore new interests or to grow intellectually.

Men, too, face a life-change when work ends. Often their career provides status. Suddenly it’s gone. For a time they must feel like the road runner after the cliff has disappeared beneath them.

Their days have been filled with challenges, with varieties of people. If a man has been accustomed to running a department or an organisation, his instinct will be to run the home. It involves a coup – and it isn’t always bloodless.

Overnight he has to shrink into a domain and a routine that must feel suffocating. No doubt many waken in wonder like Jack Nicholson in About Schmidt. He rose on one elbow, looked closely at his wife for the first time in years and thought, “How did that old woman get into my bed?”

When one of the couple talks about seeing the world together, it might not be the world the other objects to – but the together.

Fortunately, for the greater good of extended family life, most ageing couples out-manoeuvre this turbulence. Although the statistics show an increase in the over 60s divorcing, they still account for only 5% of marriage breakdown.

The planned extension of retirement age may keep a lid on it by keeping people gainfully employed for longer. But I can see why divorce in this age group might continue to rise.

After all, if marriage is for the procreation of children and the stability of family life, at 60 there is a sense of job done. It’s a natural moment for a reappraisal of marriage vows. It’s a good time to sit down and discuss what lies ahead: to explore what each partner wants from the remaining years of their lives and to evaluate whether this can best be achieved as a pair or solo.

If a couple decides to carry on together that decision will strengthen the bond. If both want a fresh start, they can part as civilised friends. That’s not to sound glib. It’s never easy to splinter a long standing union. It can turn bitter when assets have to be divided. But since conventions are changing, maybe some will settle for having a gap year – a sabbatical – and then discussing the matter again.

The saddest will be when one wants to go and the other feels abandoned at a very vulnerable stage.

I know family life also continues into a new phase. Adult children still want a stable base to which they can return for holidays or Christmas. They want a reference point for their own family life and united grandparents for their children to enjoy.

But should that deny parents the right to pursue their own goals and dreams?

For many it is a choice between a last chance at fulfilment and an empty union. Is divorce the worst alternative at this stage? Surely it is better than ending up feeling life hasn’t been lived.

Better divorce than growing old and infirm filled with rage and regret. Better divorce than 20 years lived in “quiet desperation” for the sake of – well, who, precisely?