For Bernard Hogan-Howe, the new commissioner of the Met, this will be a nightmare scenario. It was the force's flawed investigation of the racially motivated murder of Stephen Lawrence that prompted the 1999 Macpherson Report to label it "institutionally racist", leading to wide-ranging and often traumatic reforms. For the Met's critics, the fact that only one officer has been dismissed for racist behaviour since then - and that black youths remain far more likely to be stopped and searched - will fuel claims that nothing has really changed. The National Black Police Association has now called for the Prime Minister to become involved, warning that the crisis is "spiralling out of control".
The commissioner, then, has a job of fire-fighting to do - and matters will not be helped by existing strains on his resources, such as the host of officers devoted to the phone-hacking affair. While it is the force's duty to investigate all breaches of the law, it is surely wise for the Met to focus resources on an issue that threatens to do enormous damage to its reputation, and fatally distance it from the communities that it polices. Ensuring that racism has been rooted out - and that the capital is adequately protected in the run-up to the Olympics - must be its most urgent priorities.