Sir Alex Ferguson and José Mourinho have led the pleas for calm ahead of tonight’s Champions League matches involving Manchester United and Chelsea as European football seeks desperately to improve its image in wake of the shocking scenes that blighted the game last week.

With about 4,000 AS Roma fans expected to descend on Manchester today before their quarter-final, second leg tie against United at Old Trafford, and 2,500 Chelsea supporters flying to Spain for their match against Valencia, police in both cities have been put on a heightened alert.

Greater Manchester Police (GMP) are understood to be taking extra precautions as they aim to avoid a repeat of the incidents that marred the first leg in Rome last Wednesday by rating United’s match as category C, or high risk, although given the exemplary security record at Old Trafford, there are more fears of trouble in the city centre than at the match itself.

Twenty planes carrying Roma supporters are scheduled to arrive in Manchester today, although a small contingent flew in yesterday, among them Achille Serra, Rome’s chief of police, who outraged United by condoning the tactics of riot police in the Olympic Stadium and, it has now emerged, is a Roma supporter.

Similarly, the British Embassy in Madrid, in conjunction with the Metropolitan Police, have been liaising with the Spanish police on security arrangements after the clashes between Tottenham Hotspur fans and police in Seville during the first leg of the Uefa Cup quarter-final last week.

Neither Ferguson nor Mourinho are expecting any problems, however. “I don’t anticipate any trouble,” the United manager, whose side trail 2-1 from the first leg, said. “Security at Old Trafford is fantastic. I don’t think the Roma fans will have any problems. There’s never been any history of that. The policing is excellent, so Roma fans should not fear a thing.”

Mourinho, the Chelsea manager, whose team face a similarly tough task at the Mestalla after a 1-1 draw at Stamford Bridge, said: “Outside the game, I expect a positive relationship. I want Chelsea to be proud of their fans, have a beer together — no more than one — and create a good atmosphere. There were no problems at Stamford Bridge and I hope there are no problems at Mestalla.”

GMP hope that the large Italian community in Manchester will have a calming effect on both United and Roma supporters, although the calls for peace were widespread.

A statement issued by the Independent Manchester United Supporters’ Association urged fans to “wipe out the memory of those [headlines] made by the Italian Police” by showing exemplary behaviour, while Francesco Totti, the Roma captain, who is expected to play in spite of a slight back injury, said: “I hope the fans are coming here to enjoy the experience in a fantastic stadium, like we are. That’s what I appeal to them to do.”