The thing is, one feels exactly the same. Everyone says this, as they get older – as they get to, say sixty. Say, what I am. I feel the same person as when I was nineteen, when we could smoke in the cinema and park anywhere and rent a room for three pounds a week. When Diana wasn’t a Princess, she’d hardly been born, but she was alive then, and so was John Lennon . Not just alive, but wriggling in a sack with Yoko Ono. I remember this because I happened to be there at the time, at the Albert Hall when he and Yoko were on the stage, and things got out of hand, the music grew wilder and people in the audience started taking off their clothes until they were naked, and I thought, this is the sixties, I’m here and I’ll remember this moment for ever.

Which I do. But I also remember the Stones playing in Hyde Park, Mick Jagger in that silly dress, and though I can picture it in detail and smell the incense, I wasn’t there, I’m sure of that. But it’s just as vivid, almost more so.

I’m thinking this as I walk across the park this beautiful Sunday morning. How I’m still the same person I was forty years ago. I still like lipstick, and intelligent men, and potatoes. I’m still terrified of spiders. Nothing’s been solved, nobody’s the wiser. There’s just been this huge accumulation of memories, real and imagined. I’ve lived so many fantasy lives with people I’ve met, so many men I’ve been married to in my head and we’ve had six children and gone to live in the Quantocks, or wherever, in houses I’ve glimpsed in estate agents’ windows, and those lives are so potent I can smell the honeysuckle, drenched by rain, as if I was brushing past it now.

I was up early this morning because I couldn’t sleep. Last night I had a disastrous date with a man I met on the internet. A Professional Man, he called himself. I think I prefer the amateur ones. He also said he had a good sense of humour, a sure sign, of course, that he hadn’t . After the first sip of wine I knew it was doomed. A shared liking of log fires wasn’t enough for a lifetime’s commitment.

I only went because my daughter bullied me. She’s like Mrs Bennett in “Pride and Prejudice”, she wants to see me settled. She lends me her silky top and pushes me into the unknown, to sit in gastro-pubs with men whose wrinkles mirror my own mortality. We look at each other with a jolt and think that’s how the world must see ME now. These men too will be children of the sixties, these men who’re thinning on top and who hold in their tummy when they get up to go to the loo – as I do too, of course. We’ve tried to paper over the cracks but it’s like looking round a house with many previous owners; once you move in you’ll discover the dry rot . It’s always hopeless, or disastrous, and I vowed this morning that I’d never do it again.

Besides, you can’t arrange for love. It’ll happen when you least expect it. My friend Annie has fallen for a young Croatian who came to fix her boiler. She spends her evenings in a sort of dormitory, filled with his fellow-countrymen, somewhere near Luton Airport, eating cold pasta from plastic bowls. She’s blissfully happy

My friend Julie, however, believes that fate needs a nudge. “Get a dog” she says. “That’s the way to meet men. You’ll bump into some hunk with a schnitzel, or whatever they’re called. Or you could save the money and just get a lead and shout into the bushes.”

The thing is, men of my age have disappeared like the London sparrows. They’ve run off with younger women, predictably enough their secretaries or else Russian girls who bat their eyelashes and behave like Carole Lombard in some black-and-white movie, the minxes. Even the notorious adulterers have hung up their spurs and returned to their long-suffering wives.

But that’s all right. I’m fine. I don’t need anyone. And the park’s so beautiful it stops my breath. There’s something about September, isn’t there? That low sunlight slanting through the bleached grass, that elegiac sense of summer ending but not yet, not just yet… I used to think sixty-year-olds were at the November of their lives but funnily enough I’ve changed my mind now. September’s our month. We’re still the same people, us Freedom-Passers, but with a certain elegiac glow to us, a certain sun-warmed maturity. Our attraction comes from our deeply-lived experience and our bodies are fine, go on, have a look and see. Who wants the dumb blonde of May?

Quite a lot of people, I’ve discovered.

I’ve walked into the park from the Bayswater Road. The joggers are out early. They pound along, glugging water from plastic bottles. Why does everybody drink water all the time? We never drank any. The Americans, sleek young bankers, push their offspring in those monster three-wheelers that are almost as annoying as those vast 4x4s I bet they drive, clogging up the streets and squashing cyclists.

Oh dear, I’m starting to sound irritable. I’m not, of course. I’m still the same warm, lovely person I’ve always been. There’s just more to be irritable about, isn’t there? Newspapers strewn all over the Tube, people bellowing into their mobiles. Brainless celebrities I’ve never heard of hogging the TV, eight thousand channels and nothing to watch except people cooing over their blithering garden decking, serve them right now house prices have collapsed, and don’t even start me on digiboxes freezing and videos not recording and laptops crashing and printers jamming and great spaghettis of skart plugs all over the place, what are they all for? What it’s all about, Alfie? And charities sending me biros that make me feel guilty and don’t work anyway why don’t they spend the money on world peace? And spam emails offering me a better sex where did they learn their grammar, or have they found an entirely new gender in cyberspace? A better sex, indeed, chance would be a fine thing. And parking wardens everywhere but never any police. And nasty dogs all looking like pit-bulls with bowed legs, where did all the Airdales go?

No, I’m not irritable, not really. Catch me being a tut-tutter. Catch me growing into one of those whiskery crones who glares at teenagers. Here I am, striding across the park in my silver trainers, us sixty-year-olds, we’re the children of the revolution, we’re like Joanna Lumley though not so gorgeous, we’re making it up as we go along. Look at us, having affairs with younger men! Sending YouTube clips to our long-suffering children, who’re trying to get on with their work! Nobody can call us fuddy-duddies!

I’m thinking this as I walk across the park. Actually, my trainers are starting to hurt. As you get older the soles of your feet begin to burn, God knows why. It’s one of the things nobody tells you about. Through the trees I can see the Albert Hall. Last night was the Last Night of the Proms. I think of all the music that has been played there since John and Yoko wriggled in their sack. It got so chaotic that the management turned off the power. The music stopped, the lights went out and the audience subsided into a sort of stoned embarrassment. The boy I was with, who had half taken off his t-shirt, put it back on. He’s probably a grandfather by now.

I cross the bridge and walk through the area where they’ve let the grass grow long. I love it here, where it’s wild and secret. In places the grass is flattened where people were picnicking last night. I imagine them lying here as the sun set, lovers lying in each other’s arms while the music drifted through the trees and I was stuck in the pub with my Non-Smoking Professional Man, a date that had had to be rescheduled because one of his teeth had fallen out. There’s a secret glade here, my favourite place of all, where you could be in the country, the birds singing, the traffic a distant hum –

I stop dead. The grass is strewn with rubbish. Not just one or two bottles – an explosion of garbage from somebody’s picnic. Fag packets, crisp packets, beer cans, chicken bones, half-eaten tubs of coleslaw, half-gnawed ribs, sweet wrappers, plastic bags, a wine-sodden copy of Heat magazine…

I stand there, seething. All right, I admit it. I am a tut-tutter. I feel a flush rising. Not a hot flush this time, though I get plenty of those. A flush of pure, righteous anger. How could they, whoever they are? How could they ruin this place, the drunken slobs?

So I pick up one of the carrier bags and get to work. A few years ago I would have been too self-conscious to pick up somebody else’s rubbish but age brings a certain freedom – you no longer care what other people think. Or, not quite so much. Anyway, a little bit less. Besides, there’s nobody around anyway, so that’s all right.

I start shoving the garbage into the plastic bags. It’s still damp with dew, or maybe slime. Cranberry juice still slops around in a sticky plastic bottle. Ants have invaded the coleslaw and a small black slug has left a trail of mucus across a photograph of Paris Hilton. Various celebrities are shown stumbling out of nightclubs but she’s the only one I recognize. My daughter says I needn’t bother learning their names. In fact, even she doesn’t know some of them; that’s how old she has grown, seemingly overnight, without my even noticing.

As I shove in the rubbish, tut-tutting away, I speculate on whose picnic this is. There’s an empty Rizla packet, so they must have been smoking dope. Kids, probably, but not the sort who would be singing Land of Hope and Glory at the Proms.

And then I see the mobile. It’s lying on the grass next to an empty bottle of Valpollicello. I pause for a moment. A mobile eh? I pick it up. It’s damp; I wipe it on my jumper. It’s a sleek, fancy mobile, a newer model than mine. A very nice mobile, in fact.

Well well. Now what? A fly buzzes over the remains of the food. I feel something shift inside me. I should give it back, of course. I should find out who it belongs to and return it to its owner.

My blush deepens. Of course I should give it back. If I keep it, I’m transformed from a good citizen into a thief. I stand there, considering this. But does this sort of litterbug deserve to get their phone back? Aren’t other people more deserving of such a mobile – people like myself, in fact, whose own mobile is so ancient that it hardly works at all? Better still, my son, who’s a teacher in an inner-city school and who’s spending this sunny weekend stuck in his dingy flat preparing for another term of dodging flying knives, and whose own mobile has packed up completely?

I open the phone and scroll down the list of names. Chloe. Zoe. Bella. Leo. Zak. Zak! They’re middle class! No wonder there’s a pot of tabouleh amongst the mess. Besides, you have to be well-off to live round here. This makes me seethe even more. I can just picture them, these priviledged kids who should know better. Chloe would be loungeing on the grass, all long tanned legs, fiddling with her ipod. Leo, rolling a joint, will be trying to get off with Bella, who’s ludicrously beautiful. Zak’s parents will be in the media, of course. I’ve taken a particular dislike to Zak. Zak got straight A’s but that’s because he went to private school, like the rest of them. Throughout the future, doors will open for these young people. Blithely, obliviously, they’ll sail through life, leaving their rubbish behind for somebody else to clear up. Somebody like me.

I know! I could text them all and arrange a meeting in some pub. When they arrive, Zoe and Chloe and Zak, they’ll find nothing there except a pile of bin bags!

I look at the names again. “Mum” is at the top. There’s her phone number. I have a good mind to ring up Mum and tell her what a litterbug she’s got for a daughter, why didn’t she bring her up properly? By now I’m pretty sure the mobile belongs to a girl. My suspicions are confirmed when I click on the Outbox and read the most recent message. It is indeed to Mum. Please check I switched off my hair straighteners. Spelt funnily of course, in text-speak. Suddenly I feel a wave of sympathy for my fellow mother, wading through the cesspit of her daughter’s bedroom searching for a pair of straightening tongs. I know it, I’ve been there.

And the poor woman is obviously divorced. “Dad” is a separate entry. Maybe Mum’s still reeling from her husband’s defection. Dad has run off with his PA, who is of course younger and prettier than Mum. He has two numbers: Dad Mob and Dad Work. Maybe I should phone him. Maybe it’s Dad’s fault that his daughter has become such a delinquent. She’s deeply unhappy, she’s seeking his attention. She feels that she’s the rubbish, discarded by the father who has abandoned her.

But then, perhaps I’m wrong. Perhaps it’s Dad who’s the victim in all this. Mum has fallen for a Romanian minicab driver and chucked him out. Dad’s now languishing in a bedsit above a launderette. Maybe I should phone up Dad. We could moan about our divorces. Moaning is very bonding…quite erotic, in fact. We arrange to meet, so I can hand over the phone, and one thing leads to another…as Annie says, love comes when you least expect it.

Suddenly, the mobile rings. I nearly drop it in surprise.

Oh God, it’s Mum, looking for her daughter who hasn’t come home! It’s the owner, hungover and groggy, trying to find out who’s got her phone!

I dither for a moment. Finally curiosity wins and I press the answer button.

A voice says: “Morning, love. Henry’s waiting for you. Have you forgotten your appointment?”

My brain whirls. Who’s Henry? A hairdresser? But hairdressers don’t work on a Sunday. A boyfriend? But you don’t have appointments with boyfriends. Maybe Henry’s a doctor who does abortions on his day off! Maybe I should phone Mum and tell her what her daughter’s up to!

I ask the voice “Er, what appointment?” And the person tells me.

* * *

Fifteen minutes later I’m sitting astride a big bay gelding called Henry. We’re trotting out of a stables, just behind the Bayswater Road, a whole group of us. I haven’t ridden a horse since I was a teenager but it all comes back to me, the years vanish and I’m young again. Look, I can do it! Now we’re cantering along Rotten Row and the old muscles are working again, my knees are gripping the saddle and Henry’s mane is rising and falling in the wind. His neck is damp with sweat, he’s a beautiful horse and I’m rapidly falling in love with him, that fierce pure passion I felt for horses before boys came along, before love affairs and marriage and divorce. The sun shines; the pigeons scatter in front of our thudding hooves. This is Flora’s ride – that’s the name of the mobile phone girl, they told me at the stables – but Flora must have overslept, she never turned up, and I’m that young girl now, just for an hour, the young girl I’ve always been despite the wrinkles. Nothing’s changed. The memories come flooding back, how I was so pony-mad that even when I wasn’t sitting on one, which was most of the time as I couldn’t afford it – even then I pretended to be riding, I cantered through the suburban streets which were transformed into forests and glades and in a weird way that was just as thrilling as the real thing. Indeed, more real.

We trot past the Albert Hall, where the signs for the Proms are being taken down. I feel a wave of affection for the unknown Flora, whose life I’m living for this brief hour. She’s got everything ahead of her, the joys and sorrows, and I forgive her the rubbish because I wasn’t so perfect myself, especially when I’d smoked a few joints, and hey ho, who cares?

Henry tosses his head and snorts through his nostrils. I wonder what she’ll be like when I meet her, this Flora, when I give back the phone. We’re united by our love for a horse, the first great passion for girls, the simplest passion of all. But half an hour later, back at the stables, I discover that the mobile has gone. It must have fallen out of my pocket while we were cantering. So I’ll never meet Flora, or Chloe, or Zak. I’ll never know my little cast of characters.

Except I do, of course, in my head. That group of friends, picnicking on a golden summer’s evening, they’re as real to me as the real thing. Whatever that might be.