In the old days, before 60 was the new 40, it was called a midlife crisis. Now, as we learnt last week, it’s called “second life syndrome”. And should I warn you, like ageing rockers opening trout farms or making organic cheddar, it’s becoming almost compulsory.

According to Standard Life, more than 10m of us have ended a relationship or switched career between the ages of 35 and 65, so Tony Blair, 54, who is heading off to bring peace to the Middle East (someone said it was like putting Dracula in charge of a bloodbank) is right on trend.

Tina Brown has invented a special term for when exceptionally beautiful, newly single, middle-youth women (especially princesses) as opposed to world leaders, do it. In her book on Diana, she noodles lots on what is effectively the same theme: self-reinvention.

“As she entered her 37th year Diana told herself she was looking for love. But what she was really seeking was a guy with a Gulfstream. Her needs at this juncture had more in common with those of second-act sirens like Elizabeth Hurley . . .”

Ten years ago, Tina reports, Diana thought that new-broom Tony would “sweep her old life away” and entrust her with a humanitarian mission. “Blair told me that he had Diana in mind to boost the Africa initiative on overseas aid and debt cancellation,” TB (as in Tina, not Tony) writes.

So in Tina-speak, those who change direction after getting divorced (from one’s job) or being dumped (by the public) are second-act sirens. And yes, second-act sirens/second-lifers, do appear to be everywhere.

Everywhere you look, people are downscaling, self-actualising, actresses and businessmen are training to be psychotherapists, Blur guitarists are becoming cheesemakers, the Spice Girls are reforming, it’s all happening, we’re splitting up, getting back together, moving to Wales, growing our own, and seriously thinking about producing English wines.

But the reasons we are doing it aren’t quite as fabulous as all this sounds.

The first is divorce. The old pattern of long-term cohabitation – meet someone, move in, raise children, retire – no longer applies. About 145,000 couples divorce every year, compared to just 27,000 in 1961. This headline figure, by the way, does not include the number of unrecorded separations among those who never married. So lots of the second lifers will find themselves in what William Higham, founder of the Next Big Thing trend forecasting organisation, calls “dad pads”, which sound like they should have wings and extra absorbency but are, in fact, the probably grim flats lived in by fathers after the forced sale of the marital home. Nice.

The second reason is the ageing population. A third of the UK population is over 50, but that is set to rise to half the population, or 30m people, by 2025. Half of us over 50. And no pension to speak of, because we’re either self-employed in our groovy creative jobs or because Gordon pinched it. No wonder we will all be carrying on working, working, working till we keel over in harness and why we need new careers until our children can finally get their hands on our houses, if they can, what with inheritance tax being what it is.

So while it may sound as if the world is our oyster, and life is replete with endless thrilling possibilities that we should grab with both hands, while we still can, what second life syndrome really tells us is this: you’re never too old to have a midlife crisis, to change career direction, to retrain, to rejoin the workforce after children. The number of oversixties working is set to double by 2020.

That comforting downtime, those sunlit uplands, when we thought we would be able to settle down in front of Wimbledon of an afternoon, with pipe and slippers and cocoa, or mind our grandchildren, is receding by the minute.

In the future, I reckon, we will always be both too young and too poor to retire. I’m on my way to Oxford, settling down to the new Adam Thorpe, when a ringtone peals out.

“Hey there,” blares an American voice, each syllable evoking joy at the prospect of a rare enforced weekday hour of doing nothing or reading vanishing. “I’m, like, on the Oxford Tube.” Far from whispering – the upper level is, until that moment anyway, quiet, full of slumbering eastern Europeans in sandals and crumbling dons with copies of the journal of electron microscopy in Tesco carriers – our interlocutor raises her voice further to announce this exciting piece of news, as if she has been hired to test the strength of the glass.

I allow myself to fantasise, as the coach rumbles past Hillingdon at 2.45pm, that the call will be brief. But the American woman proceeds to talk at the top of her voice for no fewer than 40 minutes while the rest of us maintain complete silence.

So we hear all about her new flat, the absent builders, but the main portion of the one-sided conversation concerns the delivery, to be specific the nondelivery, of her new fridge, a Maytag. To be even more specific when the delivery company finally delivered the new fridge, three months late, it was the wrong Maytag and had to be sent back.

I try turning round and glaring, during her monologue about the ice-dispenser. I even, at one point, rise in an angry schuss from my seat and tut.

She had a lovely time, of course, whingeing, but as for the rest of us, it wasn’t just impossible to read, it was impossible even to think about anything except how to kill her.

And my point? Oh yes. My point is, mobiles, and so on. Great for the user. The iPhone is probably a fantastic piece of kit, well worth days of camping outside Apple stores for, no doubt. BlackBerries? Awfully convenient, if you want your e-mails and you want them now.

But there’s a reason why the most exclusive areas of BA’s lounges are now mobile-free “sanctuaries” and it’s not just because being incommunicado is the real luxury. It’s because people who use mobiles in confined public places are (unlike now law-breaking smokers, who are always the most fun people at any party) irredeemably antisocial. They can go on, and my word, they do.

Whoever it was who said that the telephone had too many shortcomings to be considered as a means of communication was, it turns out many decades later, only too accurate.

rachel.johnson@sunday-times.co.uk

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