It did not take long for black people in Brixton to conclude that the nail bomb which ripped through their community was motivated by racism.

The police will be judged by whether they catch those responsible

Strictly speaking that perception made the bombing a racist incident right from the outset. Both the Association of Chief Police Officers and the report that emerged from the inquiry into Stephen Lawrence's murder define a racist incident by perception rather than by the motivation of the perpetrator.

Ultimately, the police will be judged by whether they catch those responsible, but there are important indicators of police actions and intentions which will be assessed en route to any arrests.

A delivery van had its door blown off by the blast

The first is how sensitively they dealt with those early perceptions of racism. This is a tricky one for the police because during the first stages of an investigation they need to keep an open mind about who is responsible.

It is no good ruling people out when it may still be that the public's help is needed to find a lone psychopath, a Mardi Gra style extortionist or some other group with a twisted, non-racial, political motive.

The police also have to avoid spreading panic and an early, explicit acknowledgement that the motive was indeed most likely to be racial would do little to calm a tense community. In seeking to reassure people Scotland Yard has drafted in its most senior anti-terrorist experts and increased the number of uniformed officers on patrol.

Scotland Yard has drafted in its most senior anti-terrorist experts

They have also kept community leaders well briefed and an appeal on Crimewatch UK has proved fruitful. It will not be lost on the black community that the police are treating the case seriously enough to highlight it on the show, even while the bomb is still receiving national press attention.