You can see him sitting in one of the massage chairs in Toni & Guy, the trendy and expensive hairdressers, waiting to have his silver locks layered and his straggly eyebrows trimmed. He should, by rights, patronise a barber more appropriate to his age – say, Trumper of Curzon Street – but the girls in Toni & Guy make an agreeable fuss around him, and the vibrating chair does wonders for the chronic ache in his spine.
You can see him at the Latitude Festival with his teenage family and his 36-year-old second wife, in her yellow Hunter gumboots and Comme des Garçons jacket. They wouldn't dream of missing Latitude; so much more civilised than Glastonbury, and you can see Bill Bailey and Hanif Kureishi rather than listen to guitar bands all day. He has, after all, been listening to guitars since he was 12 (he watched The Rolling Stones and The Beatles on the first-ever Top of the Pops in 1964) and has played several versions of the instrument since he was 16.
You can see him dropping off his seven-year-old son at day-school in Highgate. The young school-run mothers look at his mass of crow's-feet, his close-cropped white hair, his zip-fronted Reiss jacket with epaulettes, Banana Republic stone chinos and Oliver Sweeney brogues and think: this guy is Orlando's grandfather, isn't he?
You can see him at the Holmes Place gymnasium wearing a T-shirt and Fat Face surfer shorts, pounding along on the running machine with his eyes shut, iPod wires trailing from his ears. His face is taut with concentration. He could be a well-preserved 40. Only the fact that his T-shirt bears the legend "Emerson, Lake & Palmer 1974" gives away the fact that he is, in fact, 60.
He doesn't like the fact that his gym offers a "special rate" for 55-year-olds and over. He wasn't crazy about the way Saga magazine came crashing uninvited through his letter box on his 50th birthday, but he's used to it now (you put up with the adverts for stairlifts and inflatable bath seats to get the interviews with Patti Boyd and Julie Christie).
He objects to being on a mailing list that sends him impertinent correspondence about retirement benefits. He has no plans to retire, ever, thank you very much. Although if he did, it would leave him more time for playing Guitar Hero 3 on his PlayStation and thrashing his son by being note-perfect on "Smack My Bitch Up". He really really hates it when some well-meaning youth offers him a seat on the 9.03pm to Victoria.
He is, in short, one of the Groovy Old Men, an urban phenomenon that's been making its presence apparent since the turn of the millennium and now stretches across all breeds and types of hombre. Age-wise, the younger GOM are in their mid-to-late fifties (think Gabriel Byrne or Trevor Eve), they flourish in their early sixties (think Bryan Ferry and Sir Paul Smith), they become terribly distinguished in their mid-seventies (think Terence Conran and Peter Blake), and can still be found cutting a dash in their eighties (think Sir David Attenborough.) Beyond that, things get a little problematic, because of the awkward manifestations of decrepitude, and they start to disappear from view, their life's work complete.
They are cool, soigné, well groomed, well dressed. They knew about The Last Shadow Puppets before their children had heard of them, and pulled strings to get tickets to The Dark Knight at the IMAX. They worry about their health, and the environment, but not to a boring degree. They ride a Norton motorbike. They're very hard to pin down, age-wise.
The most visible Groovy Old Men may be rock and film stars, writers and public intellectuals, but they're by no means all media chatterers. They can be Paul, the chap who rewires your kitchen. Paul wears tight black jeans (at 59, he's very proud of his 34-inch waist) and has installed a thunderous 50-inch home cinema in his new, post-divorce, Southwark flat, confident that a blast of the knife-fight scene from V for Vendetta will impress lady callers enough for them to ignore the evidence of age in his strangely ochrous teeth.
Whoever he is, the Groovy Old Man is hellishly busy. At his age, he's less in mortgage hell than his younger associates. He has more disposable income, and he disposes of it with abandon. His favourite clothes are black drape jackets by Versace, and coloured shirts by Etro. He can be found hovering in the basement at Liberty, especially at sale-time.
Driven by impetuous desires, he might ring Apsley, the cut-price dandy's favourite tailor in Pall Mall, to ask them to make him a suit like the midnight-blue chalk-stripe worn by Rafa Nadal's father during the Wimbledon final. He is the classic "£50 man" who thinks nothing of spending that sum on CDs and DVDs in a Saturday trip to HMV. (He aches for a box set of Mad Men Series 1.)
He is rather precious about what he eats and drinks. Reluctant to push a trolley around Waitrose (let alone Tesco or – shudder – Asda,) he buys meat on mail order from Donald Russell (who supplies the Queen) and Brown Cow Organics (whose steak is devoured by the top acts at Glastonbury.) He buys fruit, olive oil and vegetables from Ocado, and wine from Green & Blue in south London, or Berry Bros in St James's when he's feeling flush. He would never, ever, be seen dead on an allotment.
A man in thrall to visual and aural culture, an early adopter of fancy technology, he still finds the odd evening to read a well-reviewed new novel (he's currently struggling a little with Joseph O'Neill's Netherland.) But magazines bulk larger in his life. Though he doesn't spend half the year by a pool, he takes Condé Nast Traveller to read about scuba-diving in the Maldives and camel-trekking in Zanzibar. He cannot resist the sexy gadgetry on display in T3 magazine. And he is a devoted fan of The Word.
In many ways, The Word magazine is the GOM's best friend. Its tone of piss-taking intelligence and undimmed optimism for rock music is reassuring to the fiftysomething. It says: you may have become an ageing couch-potato, watching The Departed on DVD and playing the Guillemots on your Bose speakers, but we know you've still enough life in you to enjoy contemplating lives of flamboyant excess and arguing about which was the best and worst-ever screen aliens.
"I'm not sure our readers are clinging to their youth," says David Hepworth, co-founder of The Word with Mark Ellen. "The point is, they don't believe they've ever got old. They'll do what they like until they fall down. Women, for all sorts of body clock reasons, always know exactly how old they are; but men, in their own heads, are perennially 37. What's more, they're blessed with a magical ability to look in the mirror and disregard all the evidence to the contrary."
It's so horribly true. But the ageing groover has had one thing on his side in the last decade: the kids don't mock him any more for liking rock music, or wearing Carhartt jeans or even playing a Fender Stratocaster. He has been blessed by the erosion of the generation gap: he is allowed to play Interpol or Beirut on the car hi-fi, just as his teenage children can rediscover Led Zeppelin.
Hepworth finds technology to be the great age-leveller. "One of the reasons older men have proved so influential in music in the last 10 years is that, whereas the word used to be on the street, it's now travelling digitally, and a middle-aged man with full access to communication technology can know as much, if not more, than his kids. The early adopters of the iPod were blokes of 40 and over. It trickled down to the younger generation a lot later. Wherever there's a cool toy, there's a middle-aged man trying to devise a reason why he needs it."
The evolution of man from middle-aged salary-man into tragic old git used to be clearly signposted. His sex life packed up. He stopped buying clothes for himself. He ceased to take an interest in modern music, and bought box sets of old favourites. He developed a passion for gardening, or the bowling green. He drank less, and bought a home-brew kit from Boots. He went to bed at 10pm, in order not to snooze through work afternoons. He would not welcome the prospect of a camping holiday.
In Shakespeare's classic taxonomy of human life, "All the world's a stage," he turns from the fat-bellied judge – a man in the prime of life and wisdom – into a grotesque:
"The sixth age shifts
Into the lean and slipper'd
With spectacles on nose, and
pouch on side,
His youthful hose well sav'd,
a world too wide,
For his shrunk shank, and his
big manly voice,
Turning again towards
childish treble, pipes
And whistles in his sound."
And then again, it doesn't. The Bard's "sixth age" has been re-classified as the Third Age – the period of maturity and creativity, when your children have almost flown the coop, when you become alert to your own mortality (a couple of people your age have died), and you want to try everything the world has to offer: books, music, technology, drugs, travel, sex, food. You would have tried them all before, but you didn't have the money (or your wife wouldn't let you).
The Third Age is predicated on the likelihood of your having a Fourth Age of allotment-prowling retirement – but that itself looks forward to a Fifth Age, presumably spent becalmed in a morphine-fuelled care home.
In the meantime, here come the Groovy Old Men, in their £120 Paul Smith shirts, their huge, converted warehouse apartments in Bermondsey, their iPods full of The Fratellis and Bloc Party alongside Springsteen and Dylan, their Gillette clippers for disposing of nasal and aural hair, their MySpace entries, their discreet trips to the chemist for Viagra, Cialis and "vitamin supplements," their insouciance before the raised eyebrows of women and the alarm of their offspring.
The Groovy Old Men started out as the children of post-war rock'n'roll, growing up in the Forties, Fifties and Sixties. They're probably the most fortunate generation in history. Lucky to have missed the war, most of them also missed rationing, national service and austerity. But they witnessed the initial stirrings of rock music – Elvis, Bill Haley, Cliff, Buddy – the benefits of the Pill, the apotheosis of the teenager, the rise of satire, the counterculture, the expansion of screen-based culture into the global village, the first wave of computers... No wonder Groovy Young Men turned out the way they did.
Their early role models are still pushing their luck. Mick Jagger, the Chanticleer of rock for 45 years, is an astonishing 65 this Saturday. It's a quarter-century since he memorably said: "I don't know of any rule that says you can't be 40 and stay up all night." Leonard Cohen, the gravelly bard of love and enlightenment, is the most lionised figure of the musical year, making young women tremble at his 73-year-old baritone. Neil Young, 63, knocked the crowd dead at the Hop Farm festival (my 16-year-old son said it was the best gig he'd ever attended) and has directed a documentary of his old pals/adversaries Crosby, Stills and Nash touring with him, playing songs from his Living with War album. Neil Diamond, Brian Wilson and Lou Reed came over to reassure British fans that they were capable of standing up unaided, and of singing like angels without seeming in any imminent danger of joining the Heavenly throng.
This summer has brought a rash of GOM misbehaviour. Ronnie Wood, 61, legged it to Ireland with a 19-year-old Russian cocktail waitress, until hauled home by his wife and son. John Cleese, 68, celebrated his ruinously expensive third divorce by stepping out with a blonde American dame of 34 (called Smiley), and Salman Rushdie, a world-class novelist seemingly afflicted with chronic satyriasis, got his 60-year-old arm around the waist of a beautiful twentysomething black writer called Aita.
"Just what is it about older men?" demanded an article in The Daily Telegraph. Sensing a trend, The Times has started a regular fashion-and-style column called "Mutton Dressed as Lad." This October, the trend-setting senior demographic gets its own style bible when Groovy Old Men by the radio producer Nick Baker (aged 56 this year) is published by Icon Books.
What is going on? Have we lost all sense of the behavioural conventions that come with age? "People used to think that when they got to middle age – which used to be about 40 – they had to behave a certain way, that society expected them to quieten down and have their pleasures in private, like Max Mosley," says the philosopher AC Grayling, 59. "I think that's gone, because those of us who were groovers in the Sixties, and kept on grooving, haven't wanted to grow up and become staid and set in our habits. We're trying to repudiate the idea that you have to think in a certain way just because the chronology dictates.
"All these horrible clichés, about 60 being the new 40 and so on, capture a really significant change in attitude. The next big thing, now that we've had racism and sexism, is ageism. The baby-boomer generation are looking at the prospect of having to retire and not wanting to. They're saying, 'We're fitter and healthier and richer than our parents were, we want to keep going, we got all this experience and knowledge, we know how to do things now, it's just that we're slightly less able to do them in a hurry.'"
One sign that the Groovy Old Men are winning the ageism war will be when men over 40 are seen in advertisements for objects of desire. Elsewhere in Europe, they're ahead of us: in Italy, Baldessarini perfume per uomo is marketed using the image of a suave Lothario – silver hair slicked back, silver chin-beard, cruel blue eyes – who will clearly never see 60 again but has a private jet, a lissom girlfriend and, evidently, a hell of a scent.
British companies have some way to go. They will have to convince British punters, as Groovy Old Men seek to persuade them every day, that there's more to life than counting the years.
"Philosophically speaking," says AC Grayling, "there's a long tradition of thinking that life isn't a matter of time, calibrated in seconds, minutes, hours and years, but measured in experience. You can have many lifetimes if you do lots of things, and feel lots, and respond lots; if you're open to endeavour and relationships, you can pack in many lifetimes.
"There's plenty to be done, and enjoyed and experienced at any age if you're got the health and the money – and more of us have both. I think we have a dramatically different view, now, of the shape of a human life. Its narrative sequence is potentially very different from what it used to be."
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