Whenever I see incidents such as Blacksburg I try to apply the doctrine of proportional response. They are exceptionally rare and unpredictable. Britain's tough gun control did not prevent the Hungerford or Dunblane massacres. More American children (some 3,000) may die by gunfire each year than the death toll on 9/11, far more than in any other developed country. This may be a function of a migratory society or an unstable community, though it is hard to dissociate it from lax gun laws. But it remains America's choice and America's business.

Meanwhile, Britain would do well to contemplate the soaring use of guns and knives on its streets. If the image of the American school is of armed policemen, that of Britain's inner cities is of grieving mothers and weeping girls laying wreaths on pavements. British policy on alcohol and drug abuse is more catastrophic in its consequences than in any other country, and is more lethal than America's gun laws. Barely a week passes without a report condemning the government's refusal to repeal the 1971 Misuse of Drugs Act, largely because of Tony Blair's fear of the press. His failure lies at the root of urban crime, social dislocation and prison overcrowding. The unregulated drugs market is ruled by violence as ruthlessly on the streets of London as in the fields of Helmand. Yet all Blair can do is tell the black community to "own up" to it.

I'm not sure what you're getting at about the police "removing shades of grey and uncertainty". Are the police always guaranteed to be reliable and effective?

It only hits home when it happens here.