The security operation to stop English football hooligans from travelling to Euro 2004 in Portugal has begun, amid pleas for good behaviour by fans.
Up to 60,000 England fans are expected to travel to Portugal
Dozens of officers are at airports to screen departing passengers.
England coach Sven-Goran Eriksson has warned fans the team could be kicked out of the tournament if fans misbehave in Portugal.
Meanwhile, the team themselves are flying to Portugal, ahead of their opening clash with France on Sunday.
More than half of the 43 police forces in England and Wales have officers at ports and airports checking that known or suspected hooligans are not trying to leave the country.
They will be scanning passports to make sure that the holders are not on the database of those subject to banning orders.
More names are this week being added to the list of 2,260 suspected troublemakers.
Some 50,000 to 60,000 people are expected to travel to watch England's matches in Portugal.
In a personal message to fans, Sven-Goran Eriksson
warned the England team had
been "shown the yellow card" by football's European governing body Uefa and could be sent home if disturbances broke out among supporters.
He said fans had a "weighty responsibility" to behave properly in Portugal, and said any repeat of the scenes which had "clouded" past tournaments would be disastrous.
Kevin Miles, international coordinator of the Football Supporters' Federation, said the vast majority of travelling England fans would echo the sentiments expressed by the Swedish coach.
He said: "Most of us think of ourselves as one of the biggest assets to the team, urging them on, and it would be a tragedy if an England team with the best chance of winning for years was to be denied because of events off the pitch."
Eriksson's team has been shown the yellow card
But he warned that any who were intent on causing trouble were unlikely to be put off by the manager's exhortations.
"Ninety-nine per cent of England fans always behave themselves in an exemplary manner but it's hard to be sure that people travelling with a different agenda will be swayed just by the words of Sven."
Mr Miles rejected the suggestion that law-abiding fans might be being affected by this year's security crackdown on potential troublemakers travelling to Portugal.
He said: "If that was the case I would probably have heard about it. But in fact I have only heard from one fan, who has not even been issued with a banning order, asking for help to prepare his defence."
Many of the banning orders had been issued because of disturbances at domestic football matches over the past four years, to fans who may have had no intention of travelling to Portugal to support England, he said.
Police forces have also made contingency plans to deal with any disturbances on England match days caused by drunken fans at home.
They have identified pubs and bars in their areas where England fans are likely to gather to watch matches.
They have rearranged shift patterns to ensure they can deploy enough officers if trouble breaks out and have reminded pub managers not to serve people who are underage or drunk.