Oliver Conway

In the hunt for Russian intruders, the Navy is looking for solutions.

Off the west coast of Scotland, an underwater glider, like a torpedo with wings, dives under the waves and drifts off into the darkness.

Bristling with sensors, the SG-1 Fathom is capable of patrolling for months on end.

It's designed to operate autonomously in large packs.

It's made by the German defence technology company Helsing, but it's here being trialled for the Royal Navy.

Katie Raine is the programme manager.

It's all part of a network the Navy is calling Atlantic Bastion, a system which links drones, warships and surveillance aircraft in an effort to protect vital undersea cables and pipelines.

The urgency of the project was underlined recently by the activities of a Russian research vessel suspected of secretly mapping Britain's critical undersea infrastructure, part of a wider pattern of Russian activity at sea and in the air, causing ripples of alarm across Europe.

In Portsmouth, on the day Britain and Norway announced their navies will be working together in the North Atlantic, the Defence Secretary John Healey and his Norwegian counterpart are piped aboard an experimental ship, the Patrick Blackett, used as a testbed for new technologies.

This is about keeping us ahead of the Russians.

John Healy is clear about what all this is for.

The past two years have seen a sharp increase in the number of Russian vessels poking around in British waters.

We know the threat that Russia poses.

We track what their ships do.

We track what their submarines are doing.

We know that they are mapping our undersea cables and our networks and our pipelines.

And we know that they are developing new capabilities all the time to put those at risk.

Looking on as the politicians are briefed is the man charged with supervising Britain's response, the First Sea Lord General Sir Gwynne Jenkins.

He faces a daunting challenge, keeping up with an opponent who hasn't declared war but is investing heavily and behaving aggressively.

Despite the cost of the war in Ukraine to them, they continue to put hundreds of billions of dollars worth of investment into their submarine fleets.