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The PM has vowed the UK will do everything in its power to "destroy" President Putin's "shadow fleet operation, starve his war machine of oil revenues and protect the subsea infrastructure".

In this case, it contributes to two high-voltage subsea links - one from Torness in East Lothian to County Durham, the other from Fife to landfall in Lincolnshire and on to Norfolk, while installing new substations and overhead transmission cables, often facing the headwind of local resident opposition.

With this technology, it is even possible to work out the approximate size of a vessel passing above a subsea cable, as well as its location and, in some circumstances, its direction of travel.

"The number of cable faults per year has really held steady over the last several years," she adds, explaining that the 1-200 faults that typically occur annually has not risen despite ever more subsea cables being installed during that period.

It was during tests of AP Sensing's system last year – not a real attempt at sabotage – that the diver patted his hand on the subsea cable watched over by the firm.