Visitors lingering on the bridge overlooking the submarine factory in Barrow-in-Furness can expect an unusual welcome these days. Pointing a camera on the public crossing is likely to result in an audience with Ministry of Defence police.

At a time when Russia is pouring resources into monitoring classified military sites across Europe, including the use of its shadow fleet oil tankers to launch drones over the UK, such interventions are increasingly routine in this far-flung corner of Cumbria.

An average of two or three times a day, patrolling officers perform “stop and account” interceptions whereby anyone showing more than a passing interest in the vast facility is approached to identify themselves and explain their reasons for being there.

The sensitivity is heightened by the current presence in the dockyard run by defence giant BAE Systems of HMS Achilles – the last of the Royal Navy’s fleet of seven hunter-killer nuclear submarines being built in the town at a cost of £1.5bn.

As one law enforcement officer put it when The i Paper visited Barrow this week: “The bridge keeps us busy. It’s mostly tourists – it’s a natural response when you see something like a submarine to want to photograph it. But we have to check things out.” MoD Police declined to comment.