By Charles Scanlon BBC Tokyo Correspondent

They are preparing for the worst in the Japanese city of Yokohama.

In the biggest exercise so far for the World Cup, 1,000 riot police in well drilled platoons showed how they would confront, surround and arrest fans that get out of hand.

Trained in martial arts, the police wielded an array of hooks and prongs - updated versions of weapons once used by samurai guards to subdue offenders.

South Korean police have been training too

For months, the Japanese media has been full of alarmist stories about the hooligan threat.

Determined not to be caught out, the police look as if they are preparing for a barbarian invasion. Particular attention is being paid to the stadiums where England will play their group games.

Water canon, dogs and the celebrated "net gun" - able to restrain up to seven hooligans at once - are all being tested for possible use.

Fears have been raised that the police could overreact during the tournament. The sight of hundreds of boisterous European fans advancing up a street could be interpreted as threatening behaviour by police commanders on the ground.

"There is still work to be done," said British Home Office Minister, John Denham, on a recent visit to Japan. "We want to break down the stereotype that every visiting fan is some sort of violent hooligan."

Japanese fans

The British Government is working closely with the Japanese to help them identify and deal with problems. About 1,000 known English hooligans will be forbidden from travelling and British police "spotters" will be on hand to assist their Japanese colleagues.

For the first time, though, the Japanese police have acknowledged there could be home-grown problems as well.

The host countries are getting excited about the tournament

Football hooliganism may be unknown in what is a largely peaceful and law abiding society. But teenage tearaways known as "bosozoku" - motorbike tribes - are a common sight on Japanese roads during public holidays.

In the Yokohama exercise, police acting the part of gang members confronted the lines of riot troopers.

"Football hooliganism may be new for us, but bosozoku and other local thugs sometimes take advantage of festivals to cause trouble," said Yasuo Nimi, deputy director of the police unit responsible for world cup preparations.

"It's possible that they could get involved during the World Cup and we're making preparations to counter them."

Yokohama is taking pride in its selection as the host city for the World Cup final. It is a rare opportunity for Japan's second largest city to outshine its giant neighbour Tokyo.

But pride is mixed with some apprehension as the big day approaches. In the city's only football bar on the day of the big exercise, there was an unlikely crowd - 19 young women from a nearby accounting office - and just one man.

Bars like this will be sought out by visiting supporters. And some of the women said they worried about what will happen. For the bar's manager, Takeshi Fujimoto, the World Cup is a big opportunity.

"It might be dangerous if the place fills up with Europeans, but at least half are likely to be Japanese so we should be OK - we'll definitely keep the bar open during the tournament," he said.

Yokohama is looking forward to its brief moment on the world stage - but the citizens could be forgiven for wondering just what they have let themselves in for.