Along the main street of Tottenham, a north London suburb where racial violence flared in the 1980s, police are again having to walk the beat in pairs after a gap of more than a dozen years.
Local commanders say the measure is necessary to discourage possible attacks by teenage gangs angry at the death last month of a black man in police custody. The order followed a march through Tottenham by some 600 demonstrators carrying signs accusing police of murdering Roger Sylvester.
The newly enforced alert in Tottenham is a symptom of a wider crisis of confidence now seriously straining relations between British police and the nation's 3 million-strong black community.
The crisis was openly acknowledged this week by Britain's top policeman. Amid accusations of "institutionalized racism" among officers, Metropolitan Police Commissioner Sir Paul Condon said: "Is there racism in the police? Yes. Is it more than a few bad apples? Yes."
His remarks in Tuesday's London Times are buttressing claims that all or most of the United Kingdom's 52 police forces contain officers who adopt racist attitudes.
Commissioner Condon's admission also highlighted mounting evidence that the nation's black minority, accounting for roughly 5 percent of the population, is too often at the receiving end of racial prejudice. Complaints have been aimed at institutions ranging from the armed forces to health care centers.
In the Times interview Condon said he would make it "a point of honor to resign" if an official inquiry into police handling of the murder of a black London teenager six years ago criticizes him personally. Stephen Lawrence was killed by a group of white youths, none of whom has been punished. Lawrence's parents accuse police of failing to apprehend the youths, despite having witnesses and other evidence linking them to the attack.
The results of the Lawrence inquiry, conducted by a senior judge, are likely to be published in the next few days.
Ironically, Condon has been in the forefront of senior police officers who have worked hard to root out racism and corruption. But his attempts to deal with police wrongdoing have produced only limited results.
Meanwhile, evidence of latent and persistent racism in British society as a whole continues to pile up, and it is clear that Condon and other police officers are trying to deal with only one aspect of a much larger problem.
Last year a survey by the highly respected London-based Policy Studies Institute, commissioned by the Department of Health, found evidence of widespread racism within Britain's government-funded National Health Service. It showed that ethnic-minority nurses are often racially harassed by patients, colleagues, and managers.
The report called for support for a nationwide campaign to develop a workplace culture in which racism is unacceptable.
Last November Gen. Sir Charles Guthrie, chief of Britain's defense staff, conceded that racism was a big problem in the armed forces when he told senior officers that it was up to them to show all ranks that prejudice had no place in the modern Army.
"We are fighting a war on racism," he told the officers and ethnic minority community leaders. "We do not want anyone joining the armed forces who has racial prejudice."
Condon's admission of racism in police ranks angered police spokesmen. They reject the view that large numbers of officers are prejudiced. On Jan. 29, leaders of the Police Superintendents' Association, representing senior officers, claimed the inquiry into the death of Stephen Lawrence had "vilified the police force."
Chief Superintendent Peter Gammon, president of the association, said, "Accusations of racism are being leveled at officers in the police force as a whole. We believe the accusations are unfounded."