The number and simultaneity of yesterday’s attacks suggest localised surveillance and bombmaking, requiring a local support apparatus. We can presume that the bombers spent a considerable amount of time in the UK and may have even been UK residents.

In this way and in others, the London attacks conform to post-9/11 terrorist trends. Globally we have witnessed a movement away from the centralised planning of grandiose attacks seen in Osama bin Laden’s al-Qaeda and towards independent groups attacking smaller and less protected targets. The largest recent terrorist attacks before yesterday’s — the 2003 bomb attacks in Turkey and the 2004 train attacks in Madrid — were both cases of this “homegrown terror ”. The terrorists behind these attacks were residents of these nations and appear to have acted entirely independently of al-Qaeda’s central hierarchy. While a group calling itself “the Secret Organisation Group of al Qaeda of Jihad Organisation in Europe” has claimed credit for the attack on London’s Tube, it is not at all clear if they have any real co-operation with bin Laden’s al-Qaeda or rather simply an emotional or aspirational one, or if their claim is legitimate at all.

The UK, with its highly attuned police force and MI5, has been a model for the US and other nations in terrorism prevention. Honed by years of IRA terrorism and a very well-designed counter-terrorism infrastructure, the UK, and particularly London, is considered one of the best examples of active policing used to prevent terror. Sadly, yesterday we learnt that even so, more emphasis must be placed to train and empower police and citizens to help identify and prevent terrorism.

Faced with the threat of al-Qaeda releasing weapons of mass destruction, many governments have focused on efforts to train local police and fire departments to be “first responders” to terrorism — that is, to spring into action once an attack has occurred. These efforts help the personnel to purchase expensive gear and training to be, in effect, the “clean-up crew” after a successful terrorist attack, as opposed to empowering them to be “first preventers” of terrorism — to stop the terrorists from planning and mounting the attack in the first place.

Interest in mitigating a WMD attack after it happens means that in the US we have spent less effort training police to prevent attacks like yesterday’s. This is short-sighted.

Certainly we must ensure that our police and fire officers receive such “first response” training and equipment — to mitigate the effects of an attack after it occurs — but we must also empower them to succeed at the very difficult and important task of detecting terrorists before they attack us.

Local police have unique advantages over national assets (such as MI5) to help prevent acts of terrorism because they are part of the community. They “walk the beat,” communicate regularly with local residents, and are more likely to notice even subtle changes in the neighbourhoods they patrol daily. Common sense tells us — as does experience — that local law-enforcement personnel are uniquely situated to notice (or otherwise learn of) and investigate unusual or suspicious behaviour. Based on the numbers alone, we can assume that local law enforcement personnel are much more likely than national agents to cross paths with terrorists.

Training police as first preventers also brings substantial deterrence to domestic counter-terrorism. First, if terrorists feel that all the police eyeballs are trained on them, they might look for less daunting places to operate. Second, in a post-9/11 version of George Kelling’s and James Q. Wilson’s “Broken Windows” theory of policing, officers who are taught to identify the support structures of potential terrorists are more able to create the environment in which the terrorist will not feel comfortable.

Since police have typically focused on investigation and prosecution of crime, special programmes are required for terrorism prevention. Just as a seasoned drug enforcement officer can spot signs of drug dealing or use, these programmes seek to train police to identify signs of terrorism: religious radicalism, clues of bomb-making, target surveillance and other suspicious activities.

Effective programmes also include training in intelligence analysis. The US record has been poor. New York City Police Department has had the foresight to begin these complex prevention efforts. But they have done so without much federal support. In fact, a recent study funded by the FBI actually criticised the NYPD for running its own independent terrorism-prevention operation.

So something can be learnt from the terrible outrage in London. Failure to develop and foster “first preventers” among local law enforcement leaves our cities and towns defenceless to the increasing threat of homegrown terror. Local prevention is the first — and may also be the last — line of defence before any attack.

The author served as director of counter-terrorism for President Clinton’s National Security Council and is now Manhattan Institute Senior Fellow for Counter-Terrorism.

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