Even the most formidable wave of violence can be pushed back if the political will is there

It is not necessary to subscribe to some of the more hysterical versions of what is happening with violent crime in Britain to accept that that in some places there is, indeed, a crisis.

Comparisons with the homicide rate in New York City, for example, are grossly misleading, as New York has revolutionised its policing since the 1990s, and is now one of the safer of the major world cities. The murder rate in London is, in fact, lower than for most of the recent past. London’s murder rate has fallen from 181 in 2005 to 155 in 2007, 101 in 2013 and a half-century low of 93 in 2014. Since then it has edged up, to 116 last year. Though that is a rise of almost a quarter, the absolute numbers remain extremely small.

There is, then, no cause to take emergency measures to deal with the problem. However, action does need to be taken because although the figures for the entire metropolis, like those of other big cities, are relatively encouraging, such knife and gun crime is depressingly concentrated among certain neighbourhoods and within certain ethnic groups. For them, the streets and parks of the capital do not feel safe. The threat of gang violence is real, and extremely varied.

In London, too, there has been a marled rise in the use of mopeds and acid for violent robbery. Besides, the difference between a fatal and non-fatal stabbing is often a few centimetres, or the speed at which an accident can arrive at A&E – so small variations in the figures may exaggerate the reality. Even so, when surgeons in parts of London talk about children in school uniforms appearing to be treated for gun and knife crime, then there is a need for urgent attention.

The causes of this rise in violence are necessarily complicated, but, as David Lammy, MP for some of the most notorious areas, has argued, there are some obvious factors at work, and ones that we shouldn’t feel shy about discussing.

As ever, the drugs trade is behind much of the violence, with the new “county lines” push to expand business beyond the major metropolises, using children as couriers, a new take on traditional turf wars. It is said that there are Eastern European gangs behind these activities, with a familiar hierarchical structure.

Again, as has always been the case, nabbing some hapless 15-year-old on a train to Aberdeen is unlikely to break the problem. Intelligence resources, badly stretched in the war on terror, have to be found to pursue and subvert these criminal gangs. Once they have placed their pernicious hold on some market town or smaller city, then the damage is likely to be bloody and permanent, for with the drugs from Eastern Europe and elsewhere come guns, people-trafficking and sexual exploitation too.

There is also the use of stop-and-search measures, which has been falling in recent years amid concerns about racially discriminatory targeting. Yet the mayor of London, Sadiq Khan, a dedicated opponent of racism, has identified stop-and-search as one of the primary weapons that the police can use to disrupt criminal activities at street level and to make communities safer.

Magistrates seem willing to use the freedom to set tougher sentences, but the major deterrent has to be the risk of getting caught in the first place. Again, it is difficult to avoid the conclusion that the Metropolitan Police has suffered too many cuts into many sensitive neighbourhoods to maintain the Queen’s peace, and that, rather than some supposed “political correctness”, has also been responsible for the decline in searches and subsequent prosecutions.

What is also telling is how many cases are solved relatively quickly, using local intelligence. The gangs are well known to one another, and they even take the opportunity to advertise their grisly work on social media. Arrests are relatively swiftly made and convictions are equally smooth. More often than not the perpetrators are known to the victims and, where they manage to survive, then the game is up for the (invariably) young men with knives and guns. It begs the questions as to why such local intelligence and digital footprints cannot be proactively pursued before the gangs get the chance to take another life.

The ease of detection and sometimes brazen or reckless use of lethal weaponry also suggests that many in gangs feel that time in prison is something of an occupational hazard, and that they are resigned to their fate because they have no other way to make a living. Some may believe that their vicious, dismal lives are echoing some sort of South-Central LA coolness.

Perhaps there are cultural influences at work, glamorising murder and trivialising the suffering of their victims, a nihilistic death cult that, to an extent, mirrors the radicalisation of other young and misguided men towards extremism and terrorism (on the white far right as well as among radicalised Islamists). Something in their schools or families has gone very badly wrong; it is not beyond the ingenuity of an advanced economy to attempt to correct those forces before they lead to more misery.

The experience of past crises, in New York, Manchester, Glasgow and elsewhere, though, suggests that there is no need to despair. Even the most formidable wave of violence can be pushed back if the political will, the police forces and the support of the public is there. The biggest danger for Londoners is to accept the idea that is “the new normal”. It is not in fact true, and even if it were, there is no need to accept any given level of violence as inevitable in any case.

London does not yet have a murder culture in the way that some cities in Colombia or Mexico do, nor is it likely to, but the level of lethal violence among black communities is far too high. Would not more be done if it was Chelsea or Westminster rather than Tottenham or the poorer parts of south London that felt under siege? Would the authorities then feel impelled to activate Cobra, say?

The war on gun, acid and knife crime is one that can be won, and political leadership from the top – No 10 and the mayor of London, is where it needs to start. Now.