Why we need police to tackle the terrorists

David Cameron's immediate response to the Paris terrorist attacks was to announce a significant rise in staffing and funding for the intelligence services, thus improving its capacity and capability to identify and understand the spectrum of terrorist risks.

But, crucial as it is, intelligence is not evidence. Intelligence cannot be used in courts to form the basis of a criminal case—and prosecution is the most effective way of preventing the development of long-term terrorist threats. A jailed terrorist is an inactive one. Funding the police, then, is not just a law and order issue. Police work is now central to Britain's anti-terror effort.

The scale and intensity of the terrorist threat is increasing. Seven plots have been thwarted in Britain in the past 12 months, and over 3,000 individuals require active monitoring (up from 1,600 in 2006). British police are arresting at least one person per day under counter-terrorism legislation. There has also been huge growth in the volume of electronic communications that have to be monitored for intelligence purposes. So it is perhaps not surprising that, in the case of every recent major European terrorist attack, the assailants were already known to the intelligence agencies.

This has led to the increasing use of disruption as a tactic for neutralising terrorist threats. In policing and security agency parlance, disruption refers to operations designed to inhibit terrorist plots, often without seeking a legal prosecution, by for example, blocking terrorists' access to resources, or simply by letting targets know that they are being watched. A counter-terrorism officer, whom I interviewed on the subject of the 2005 London bombings, described the potential utility of disruption to me, saying:

"There was a three-month window of opportunity before Sidique Khan and his comrades committed the attack... The reason the Service [MI5] said they weren't pursuing them was because they weren't high enough on the Intel radar. However, why didn't we just send a couple of uniformed officers to knock on the door and say 'Hi Mohammad, I'm from the counter-terrorism unit, we really need to have a chat.' Very, very powerful, that."

Disruptions, although effective, may simply provide a temporary respite, discouraging one plot only for another to surface at a later date. This is a possibility given that terrorists are not just opportunist offenders, but people with strong ideological motivations.

Faced with threats of this sort, countering terrorism has come to depend upon a blend of intelligence, policing and prevention. Most people's view of terrorism and counter-terrorism is limited to a small number of high-profile, dramatic atrocities. The more routine and mundane work of managing day-to-day terrorist risks involves both policing and intelligence-based interventions.

An intelligence-led counter-terrorism response based upon prediction, prevention and pre-emption has an understandable allure for both politicians and professionals. However, if we accept that it is impossible to intercept and interdict all threats, then we must also accept that intelligence failures are inevitable. In this case the emphasis switches to police work. Confronting the kind of extremist terror that now threatens Britain is not just a job for spies. If we want terrorists to be subject to justice in our courts, then the only people who can put them there are the police.