Emma Cook boards the police minibus in which locals comb the streets to track down their muggers
A white, unmarked minibus cruises slowly around south London's Elephant and Castle for the third time in 30 minutes. Today, the otherwise grim landmarks - lurid pink shopping centre, snooker hall and a labyrinth of concrete underpasses - hold a particular fascination for the half a dozen or so passengers on board.

They stare out intently, silent but with steely determination, to identify someone among the crowds. Since June, victims of mugging in the Walworth area have been invited to board the "victim bus" in the hope of spotting their attacker on the streets. Now running fortnightly, the operation is part of the Eagle Eye initiative launched in August, which has been criticised for creating racial tension. Detective Sergeant Vince Payne, from Walworth police station, asserts that this local scheme is not a racial issue. "We just target robbers," he says firmly. "Their colour is immaterial."

Police Constable Ray Norman, responsible for the scheme, believes that the bus offers victims an ideal opportunity to observe muggers in their natural habitat. "I'm hoping that after two or three weeks they've forgotten their crime and are not trying to hide or disguise themselves. They'll have let their guard down." Once someone believes they have recognised an assailant, they are transferred to a plain car that follows the van which then tries to track down the suspect. If the victim observes the arrest, there is no need for an identity parade.

We cruise towards the next landmark: Kentucky Fried Chicken at Camberwell Green, a notorious hang-out for "youths", according to PC Norman. "Now pay attention to where these groups are gathering, and if there's something that catches your eye, don't be shy. Just tap me on the shoulder. Remember, it's your minibus today," he tells us cheerfully.

Victims shift in their seats and stare fixedly out of the windows. As their brief memory is based on a frozen image up to three weeks old, are they sure they can remember one face among the hordes of evening commuters? "I'll never forget mine," says Jean, a pensioner in her late sixties. "He was half-caste," she adds, by way of explanation.

Unable now to be more specific, Jean is still convinced she will recognise the young man who snatched her handbag as she was getting out of a car three weeks ago. Fortunately, victims cannot be too rash, as the police take down a detailed description of the attacker before they board the bus. If they do spot someone, the details must correlate with their earlier record.

As the evening progresses and the streets start to empty, it seems increasingly unlikely the passengers will spot any suspects. "It's as if they know and have deliberately stayed at home," says one elderly man, clearly peeved. Although there have been a few identifications in past journeys, only one arrest has taken place and that was later dropped. Even if a victim does spot his assailant among the masses, by the time he taps a PC on the shoulder, gets out of the van and into the car, it's difficult to catch up with them.

Not that this seems to bother the victims or PC Norman. "The main benefit is that they've enjoyed coming out," he says, during our tea and digestives break in the police car park. Many have got so much out it, they're on their second or third trip. "They must be getting something good out of it if they keep coming back," he says.

PC Norman believes the exercise is valuable in helping to empower victims. "It gives them a chance to point the finger and take part in catching their assailant. Which must help to alleviate the frustration and helplessness you feel in that situation." It also helps to fuel a collective resentment that doesn't feel particularly constructive. "I want to see justice done," says one elderly man, vehemently. He was recently mugged outside his front door by four youths. "It's awful what they get away with - even if they do get caught it'll just be a slap on the wrist." Another woman nods her head in agreement.

Group conversation focuses on other crimes reported locally. "Did you hear about that poor woman in a shopping centre last week?" says one girl. "Oh, yes," another joins in. "The one who was whipped with a belt - big welts on her back and she was taken to hospital." We all tut and sigh with a mixture of disbelief and disgust. The climate of anxiety in the bus increases. Staring out of the window, suddenly everyone on the street looks like a potential attacker or at least blameworthy.

The evening's excursion is more about allowing victims to express their anger and resentment than actually reducing crime. At the very best, it may be therapeutic for some of the victims taking part. "They've gotta show their face sometime," says 14-year-old Karen, mugged recently by a group of girls on her estate. She stares out of the window defiantly: "I'll just keep coming back until I see them."

Victims' names have been changed.