The Home Guard Never Went Away

Anyone contemplating an attack on RAF Fairford might reasonably think the difficult bit would be getting past the RAF, the Americans, armed police, counter-terrorism officers and whatever bits of the intelligence establishment happen to be paying attention.

But Britain still possesses another, largely unrecognised, layer of national defence which no hostile planner should ever underestimate. The curtain twitcher.

Reports say the Fairford incident began when a local resident noticed three suspicious vehicles apparently heading towards the base in the middle of the night. She reportedly tried the airbase police first, got no answer, and rang 999 instead. Shortly afterwards there were armed officers, bomb disposal teams, emergency vehicles and arrests.

Which suggests that, if this does turn out to have been a serious attempted attack, somebody may have made one fairly elementary planning error. They had allowed for the RAF, the police and perhaps even MI5. They had not allowed for Brenda at No. 27, who has lived there since 1984, knows everybody's car, knows who has visitors, knows who parks badly and certainly knows when three unfamiliar vans appear in the area at an odd hour.

This is Britain's unofficial Home Guard. The original version had uniforms, rifles and Captain Mainwaring. The modern version has a fleece, a spaniel and WhatsApp, and its members are permanently deployed beside bay windows, front gates and kitchen sinks. Any unfamiliar van is logged, any stranger standing about is noted, and any unexplained activity is mentally filed for possible discussion over the fence.

A hostile intelligence service might spend months studying CCTV coverage, police response times and electronic surveillance. All wasted, because nobody has yet invented a countermeasure to somebody saying, "That's funny. I've never seen that van before." You cannot really jam it or spoof it, and once Mrs Miggins has mentioned it to Derek over the fence, the intelligence has already been disseminated across the entire sector.

Within minutes somebody will have checked the village Facebook group, somebody else will have taken a photograph through the curtains, and a retired bloke called Geoff will have walked past twice with the dog for reconnaissance purposes.

The Americans have stealth bombers and MI5 has surveillance teams. Rural England has people with absolutely nothing better to do and an encyclopaedic knowledge of who belongs there. That may turn out to be rather more useful than it sounds.

During the Second World War we armed the Home Guard because invasion was expected. We have since refined the system. What really mattered was not the rifle so much as the deeply rooted British instinct to notice somebody doing something they shouldn't and immediately tell somebody else.

So if the suspicions surrounding Fairford eventually prove justified, the lesson for any future would-be saboteur is fairly simple. By all means plan for the perimeter fence, the cameras and the police. Plan for MI5.

But for God's sake, plan for Brenda.

Because the last line of British national defence is still sitting behind a net curtain thinking:

"Who the bloody hell is that?"