A Russian naval ship is currently sailing 30 miles off the British coast, close to an offshore wind farm which powers more than 400,000 homes.
The Kremlin's Amur-class repair ship PM-82 is currently located around the Galloper wind farm off the coast of Suffolk.
The 122-metre floating workshop is designed to maintain Vladimir Putin's Baltic fleet of warships.
It is the latest move in Putin's 'grey war' with the UK and the West, after sailing through British waters and mapping undersea cables.
Last week the head of the Royal Navy warned that Russian incursions into UK waters had increased by a third in just two years.
General Sir Gwyn Jenkins said: 'In 2025 alone the Royal Navy was required to respond dozens of times, pitting homeland defence against Russian Navy vessels.
'It is Russia's investment in its submarine programme that poses the most acute threat. Our submarines are spending a substantial amount of time responding to Russia subsurface activities.'
The Russian repair ship is designed for the upkeep of its warships and submarines, with 18 believed to be in the Russian navy.
The Kremlin's Amur-class repair ship PM-82 is currently located around the Galloper wind farm off the coast of Suffolk
John Foreman, the UK's former defence attaché to Moscow, told The i, the ship may be 'waiting to escort' sanctioned vessels through the region to make the 'chances of UK action' to seize the illicit ships 'even more remote'.
Commander Arlo Abrahamson, spokesperson for Nato's Allied Maritime Command said that the military alliance was 'watching these activities closely and sharing information with our allies to assist their efforts in monitoring this vessel'.
He added: 'Allied Maritime Command operates as a maritime hub for the alliance and our objective is to enhance maritime situational awareness in waters throughout the Euro-Atlantic.'
This morning the British anti-submarine frigate HMS Sutherland was sent out to observe the Russian ship.
On Tuesday morning, eight sanctioned tankers suspected of aiding Moscow's illicit oil networks passed through the English Channel.
The repair ship was seen in the exact same spot last month, sparking concerns that Putin is targeting UK critical infrastructure at sea.
There are concerns that the ship could have been in the area as a makeshift bodyguard for Russian shadow tankers operating close to Britain, in a bid to prevent them being boarded.
It comes after Russian navy vessels, including submarines, mapped UK undersea cabling in the North Sea for longer than a month.
Defence Secretary John Healey said a nuclear-powered attack submarine and two spy submarines had been spotted in the North Atlantic, with a warship and aircraft deployed in response.
Addressing the Russian President, Mr Healey said: 'We see your activity over our cables and our pipelines, and you should know that any attempt to damage them will not be tolerated and will have serious consequences.'
The submarines had been within the UK's exclusive economic zone, which extends up to 200 nautical miles – about 230 miles – offshore, but not within Britain's territorial waters, within 12 nautical miles (13.8 miles) from the coast, the Defence Secretary said.
The HMS Sutherland and the Russian PM-82 seen near the Galloper wind farm in British waters
British anti-submarine frigate HMS Sutherland was sent out to observe the Russian ship this morning
The operation lasted more than a month, but no damage to the cables was sustained, he confirmed.
Last month, a Russian warship Admiral Grigorovich was seen accompanying two shadow fleet vessels past Britain's south coast.
The government said Britain was ready to start intercepting members of Putin's shadow fleet as they pass through the English Channel, but no ships have yet been boarded.
Other countries, including the US, France and Germany, have previously seized Russia-linked tankers.
The Ministry of Defence has been contacted for comment.