A very indecent proposal

It is just before midnight on a crisp, clear night in Mayfair. One or two couples are walking arm-in-arm back to their cars after dinner, collars turned up against the chill wind, but for the most part, the dimly-lit streets between Berkeley Square and Park Lane are quiet.

I'm walking slowly westwards along Curzon Street towards the Hilton hotel, when a dark BMW pulls up beside me and the electric window on the passenger's side edges slowly downwards. The driver is an attractive blonde in her late thirties, dressed in a short, brown leather skirt and cream blouse, her hair carefully coiffeured and her make-up perfectly in place.

For a moment, just for a moment, I'm convinced that she is from out of town and she is going to ask me for directions - to the Westway, or Knightsbridge. And as I bend down to ask if I can help, I'm about to say: "Where exactly are you looking for?"

But I couldn't be more wrong. She bends forward across the passenger seat so that her blouse gapes open, and asks softly: "Feeling lonely, darling?" I've just become the latest victim of a new spin on the world's oldest profession.

Regardless of the dangers that stalk prostitutes everywhere, and which may well have cost three their lives in East Anglia over the past two years, the ladies of the night who once walked London's streets - waiting for men to stop their cars beside them - have turned prostitution on its head. Now it's the prostitutes who are kerb-crawling for clients.

"Sorry," I murmur to the BMW blonde. She shrugs gently and says: "Maybe another time." The electric window slides up again to keep out the night air and the automatic 3 Series glides away.

Two minutes later exactly the same thing happens all over again. Only this time it's a red Ford Fiesta, and there are not one but two women in the car. An older woman is driving, and her companion looks young enough to be her daughter.

And again, just for a fleeting moment I'm convinced that they must be lost, too. Surely lightning can't strike twice within five minutes? But I'm wrong.

The older woman leans across her leather- skirted passenger and blatantly asks: "Interested in a little business? The flat's not far." Then her young partner mouths the phrase: "I really want to f*** you." Though worldly wise, I find this shocking and unsettling. The thought of accepting couldn't be further from my mind. I turn the offer down flat. But instead of the BMW blonde's graceful exit, this pair seem to take offence. The older woman shakes her head angrily and the younger mouths an obscenity at me, before the car takes off towards Park Lane.

Both roadside encounters are a brief glimpse of the sleazier side of London that exists in the streets that are home to Annabel's, the Ritz and Harry's Bar. Just recently, reports of the kerb- crawling exploits of Mayfair's prostitutes have surfaced, and yet none of the local authorities seem particularly concerned.

Some of the girls are earning up to £4,000 a week and one even used the money to have her children privately educated in Switzerland.

The evidence is there on the street. It's now after midnight and when the third car stops, I'm ready. It's a Nissan Micra this time, and the attractive brunette behind the wheel doesn't have to say a word. "How much?" I murmur. "£250," she replies, and leans across to open the passenger door.

"No I'm sorry," I say. "I don't want to hire you, I'd just like to talk to you." I watch a scornful look spread across her face. "That's what they all say, darling."

"No, really, I'm a writer and I'd like to find out why the girls of Mayfair have taken to their cars."

She says firmly: "I've got a living to earn and I can't waste my time talking to you - specially not when you're outside the car and I'm sitting in it. Draws too much attention to us, doesn't it? I don't want to get nicked again."

"Well could I just have 10 minutes?" She looks a little uncertain. But finally nods and pushes open the passenger door. "You getting in or not?"

The moment that I do she sets off rapidly along Curzon Street. "Why the change to cars?" I ask. "It's warmer for a start," she says, before turning into a mews tucked away behind the Hilton. "Besides, it's a hell of a lot safer if you're driving rather than the punter," she adds. "You're more in control." She turns off the ignition. "You can always drive them to the nick if they're difficult."

How many clients does she have a night? "Depends," she says, running a hairbrush through her hair. "On a good night, maybe half a dozen; bad night, two or three."

Where does she take them? "Back to my flat mostly, or their hotel if the security's not too tight. But it'll cost them a grand if they want me to stay the night." She refuses to tell me her name, exactly where she lives, or how long she has been what the Metropolitan Police now call - in these politically correct times - a sex worker. "Don't want to make myself too public now, do I?" she says with a wink. "Now do you mind if I get on?"

As I have already discovered, this thirtysomething, with her tired eyes and forced smile, certainly isn't alone in working the streets of Mayfair in her car at night.

Sergeant Shaun Willshire of the Met's street offences unit estimates that there are currently between six and eight women regularly kerb-crawling the area for clients, "although you may not see any for several nights in a row".

Sgt Willshire, a police officer in central London for more than 20 years, explains: "People may be shocked but the vast majority of the sex workers in Mayfair use cars these days. Only two or three are still walking the streets. Twenty years ago there were three times the number of girls, and only one was using a car.

" Mayfair's not like Sussex Gardens or Soho, though. These women aren't going to be entertaining clients behind the bushes or in dark alleyways. They, and their clients, are more discerning. A girl can earn double what a Soho prostitute can make in the same period of time, because the clients are prepared to pay more. The men on the streets of Mayfair don't want to risk using their credit card to phone an escort agency because their wife or their office might find out. They prefer the anonymity of cash."

One of the Soho girls, says Sgt Willshire, borrowed a friend's car recently and started to work in Mayfair with punters who are almost all businessmen, many of them from the Middle and Far East.

"But I don't think that's a particular trend," he says. "Unlike Soho, the Mayfair girls are almost all British, many of them have children, and very few of them suffer the problems of drug or alcohol dependency that are common in so many prostitutes.

"They simply can't afford to be charged with driving under the influence of drink or drugs. That could mean risking a prison sentence, which they won't get for soliciting. One of the Sussex Gardens girls took to driving for a while recently - but she forgot about her problems with alcohol and ended up being arrested for drink-driving.

"And the Mayfair girls don't usually give their money to a pimp. One told me not long ago, 'No man's taking my money off me,' and she was very annoyed at the suggestion that she might be giving her money to anyone. The going rate is at least £200. One I arrested the other night told me that a client had tried to persuade her to take £100. 'I don't even get out of the car for £100, darling,' she told him."

In addition to the Mayfair girl who used her income to educate her children in Switzerland, another has bought property "as an investment against her old age", I am told.

The girls' activities offend many local residents. "It has happened to me twice in the last six weeks - once from a BMW and once from a convertible," says public relations expert Nigel Massey, whose office is in nearby Savile Row. "I was very shocked indeed. I went to the window of the car a complete innocent. It's just not what you expect.

"I'm deeply saddened that Mayfair's great name is being so badly tarnished. Someone should certainly do something about it, and I know that many of my fellow Mayfair residents feel just as upset as I do."

Some are more relaxed, however. The Reverend Penny Rose-Casemore, who has worked with prostitutes in south London, insists: "The Church is not there to sit in judgment on either the prostitutes or their clients. All humanity is precious."

But being a working girl on the streets of London - in a car in Mayfair in 2002, or on foot in Whitechapel in 1888 - is not, and never has been, anything but a sad and dangerous occupation. The shadow of Jack the Ripper hangs over each and every one of them.