It is 9.45pm and police are called to reports of a fight between 40 youths at the Fiveways Grill, a late-night cafe/restaurant halfway up Ditchling Road, Brighton.

When we arrive, staff tell officers one of the teenage boys leapt across the counter and head-butted a man twice his size.

The boy, who appears to have been drinking, is handcuffed, arrested and taken to John Street police station.

This is the kind of behaviour many older people expect of teenagers today.

Barely a week goes by without a highprofile story about yob violence or a youngster being given an Asbo.

But a night with Brighton's specialist policing unit suggests this level of violent behaviour is far from the norm.

On Friday nights a team of police officers and police community support officers hits the streets in and around the city on Operation Prince to clamp down on drinkfuelled misadventure by under-18s.

They usually end up confiscating about 20 bottles of wine and 20 cans of beer and cider from underage drinkers. The alcohol is destroyed and the youths sent packing on buses home.

Anyone found drinking illegally or acting antisocially can have their details recorded and a letter may be sent to their parents.

Most are mortified to discover how their little darling was behaving on Friday night and soon put a stop to future shenanigans.

Meanwhile, there are measures police can use to control the real troublemakers, including giving out yellow cards which mean next time an offence is committed the culprit could be arrested.

The night begins at 4pm with a briefing about which hotspots officers should focus on and which young troublemakers they should look out for. There are outstanding Asbos against five young men and each officer is handed a list of the terms.

If the offenders are found socialising with more than three people, drinking in public, being abusive or otherwise causing a nuisance, they could be arrested.

From 5pm to 8pm is the twilight time, when young people are likely to be at a hidden spot doing their best to get drunk.

Patrols go out on the streets visiting known spots for under-age drinking, such as The Level, Queen's Park, Pavilion Gardens and under the piers. The aim is to seize alcohol from young people before they have a chance to get drunk.

If groups are spotted drinking alcohol on buses on the way in, Brighton and Hove Bus Company will inform officers so they can be waiting when the bus stops.

Inspector Laurence Taylor, who heads the neighbourhood specialist team responsible for central Brighton, said: "About five months ago we had a recognised problem with young people and antisocial behaviour.

The problem has reduced massively.

"We set the tone for the evening and disrupt antisocial behaviour for youths and for people using the city to make life more enjoyable for them.

"Antisocial behaviour is behaving in a manner that isn't committing criminal offences but just being a nuisance.

"We are not saying they can't have a good time. It is important we get out and make sure antisocial behaviour is nipped in the bud. It is only a real minority of kids that cause a problem."

Mr Taylor has his own pet theory, where young people are distributed like a dart board, with the hardened troublemakers at the bull's eye. In the inner circle are those who will follow the leader and act up in public but will respond to the intervention of the police.

In the outer board are youngsters who might drink but who are easier to reach and can be directed home by the police.

Mr Taylor said: "If we can get rid of that outer group, from a police point of view it makes it a lot easier to deal with.

"Historically, the police have been about enforcement. From a community point of view, this is about crime reduction."

The hoodie factor means a lot of older people are suspicious of young people without justification - they are young, therefore they must be up to something.

Chief Inspector Dave Miller said: "If people just speak to them, you realise they're just bored. It is what they do and how they dress.

"We don't have a big problem. It is the perception rather than the reality.

"If there are people causing problems, I feel people are afraid to speak to them. You often find they're not up to much. Because of the hoods, you can't see people's faces. It can be intimidating, especially at night."

The police have been working closely with Brighton and Hove City Council's youth and connections service, which aims to find other things for young people to do at weekends rather than hanging round on the streets.

On Fridays from 6.30pm to 9pm, youth workers patrol city hot spots such as Churchill Square, joined by project workers from the Odyssey drug education project, a partnership between Hove YMCA and Brighton and Hove Youth Service.

They offer information about drugs, alcohol, sexual health, relationships and self esteem.

Louise Hawkins, a youth worker from the council's children and young people's trust, said: "There is not a lot out there on Friday nights. They get to a certain age and they feel they're too old to go to a youth club. With us, it's a lot less formal."

Emily Spilller, from Odyssey, said: "A lot of people will make assumptions about young people.

"There is quite a negative image. Often they're just meeting friends."

She said if the workers come across young people drinking alcohol, they will not tell them not to drink or force them to say where they got it.

"The last thing young people need is more teachers saying do this, do that. One reason they listen to us is because we're friendly."

PC Chris Hobden, who usually pounds the beat in the Bristol estate, Queen's Park, Tarner and Kemp Town areas of Brighton, said: "If there are groups of kids, we can just talk to them.

"Ninety-nine per cent are happy to just have a laugh. It is a novelty to talk to us and find out we're human."

At 6.30pm, a call comes in to say there is a group of youngsters throwing eggs in Meadowview, on the Moulsecoomb estate, and they have cracked a window.

Ten minutes later, there are reports of young males drinking alcohol near the Palace Pier and causing problems. Officers are sent to talk to them.

A worried resident phones police at 7pm to say there is a group of young people in the park in Rottingdean behaving badly.

Officers confiscate alcohol from the group and ensure they all get on a bus home. They will join the 700 young people who have had their details taken by the police so a letter can be sent to the parents.

Since then, 90 per cent have not come to the attention of the police again. Just last week, one anxious mother phoned to thank officers for confiscating alcohol from her son.

Patrols keep an eye on the forecourt outside Churchill Square which seems to act as a magnet to those aged 13 to 17 long after the shops have closed.

Officers carry out stop-and-search checks on a group of lads who run when they see the police.

Nothing is found on the four boys, aged about 14, and they are handed a form to explain why they were stopped.

Outside McDonald's, where a young man has been threatening staff, more boys are searched.

The 14-year-olds are eating bags of sweets. In their pockets are tickets to see the new Rocky film. Polite to the police, they are allowed to go on their way.

Thanks to a policy introduced by Chief Superintendent Kevin Moore, there are more high visibility patrols and officers are regularly on the beat in practically every part of the city.

At 9.45pm, reports of a fight between 40 youths take police to the Fiveways Grill. As we arrive, many youngsters slink off into the night. One boy is identified by staff as having attacked a worker and is arrested on suspicion of assault.

The group tell police they are from Whitehawk but are visiting their girlfriends in Fiveways.

Police instruct them to get on a bus home. Often this ends with officers waiting to make sure they do leave the area. PC Hobden admits: "Sometimes you do have to babysit them."