The announcement, within hours of another fatal shooting of a teenager in South London, that the Metropolitan Police are to deploy more armed officers in the worst gun crime areas, to check suspicious cars and set up a task force to investigate the recent killings, is both welcome and belated. Sir Ian Blair, the Metropolitan Police Commissioner, said he was “absolutely determined” to stop the appalling escalation of shootings, especially among young black males. He has already asked John Reid, the Home Secretary, to enforce a lowering of the age, from 21 to 17, at which the five-year sentence for carrying a gun is mandatory. In coming weeks he should hold urgent talks on reinforcing Operation Trident, the 300-strong squad set up nine years ago to deal with black-on-black crime. He knows well that many Londoners see the criminal violence engulfing whole communities as an affront to contemporary social values and a return to barbarism.

Grasping the scale of the issue is not difficult. Gun crime has risen inexorably in the past two decades — despite a dip of 14 per cent last year. But it is highly localised, and involves the Afro-Caribbean population disproportionately. Four conurbations — London, the West Midlands, Greater Manchester and Nottingham — account for more than half the total. Between 2001 and 2005, 63 per cent of all murders and attempted murders with firearms in London involved this community. And the age of those involved has been dropping, with most murder suspects in the 16-25 age range. The killing of three teenagers within ten days comes after well-publicised warnings for at least two years by police and social workers that easy access to guns, grinding poverty, the grip of drugs on some drab estates, unemployment, the growth of gangs and an embedded culture of criminality were creating a chronic, violent underclass.

The causes accelerating this downward spiral are as clear as they are controversial. At heart is the breakdown, or often complete absence, of family structure, especially within the black community. Much work has been done, often by black sociologists who have risked the opprobrium of community “activists”, on the disastrous absence of fathers, who do not know, care about or pay for their children and who leave young black males without any role models, at home or at school, to instil values or a sense of self-worth. Studies have also shown that young men in deprived areas see crime as a better career opportunity than legitimate work, and that drug dealing gives those with little education a change to gain the wealth and status they crave. Social pressures to own fashionable clothes, flaunt wealth and win “respect” are exacerbated by gang membership and the role model of “successful” criminals proving crime to be more lucrative than work.

Breaking these patterns is difficult. Some things must change fast. Replica guns must be banned. The incitement to violence in rap music must stop. The police must not pussyfoot around the race issue, nor naive liberals excuse appalling teenage violence by citing deprivation. It is not just a question of money: millions have been spent in Brixton and elsewhere in South London since riots 20 years ago. It is a question of changing a culture, with zero tolerance of even petty crime, confiscation of criminal assets, curfews, and above all holding to account feckless parents and criminal role models. Only then can police hope to prevent the brutal murder of boys in their beds.