The chief of the defence staff has warned of a new threat posed by Russia to communication and internet cables that run under the sea.
Air Chief Marshal Sir Stuart Peach said the vulnerability of these communication lines poses a "new risk to our way of life" because if they are cut or disrupted there would be an immediate and "potentially catastrophic" hit to the economy.
As Russia modernises its navy and perfects unconventional and information warfare, the UK's most senior military officer said Britain and NATO need to prioritise protecting their undersea lines of communication.
Conservative MP Rishi Sunak warned earlier this month that a successful attack on the UK's network of undersea communications cables could deal a "crippling blow" to the country's security and economy.
His Policy Exchange report highlighted the way that during the annexation of Crimea in 2014, the Russians "easily" cut all digital communications from the peninsula, and warned a successful attack could be carried out by a fishing trawler as well as submarines.
In his annual lecture to the Royal United Services Institute in Whitehall, the chief of defence staff said:
"In response to the threat posed by the modernisation of the Russian navy, both nuclear and conventional submarines and ships, we along with our Atlantic allies, have prioritised missions and tasks to protect the sea lines of communication.
"This sounds like a re-run of old missions. Actually... it is very, very important that we understand how important that mission is for the North Atlantic Treaty Organisation (NATO).
"Because Russia, in addition to new ships and submarines, continues to perfect both unconventional capabilities and information warfare.
"And there is a new risk to our way of life, which is the vulnerability of the cables that criss-cross the seabeds.
"Can you imagine a scenario where those cables are cut or disrupted, which would immediately and potentially catastrophically affect both our economy and other ways of living?
"We must continue to develop our maritime forces with our allies, with whom we are working very closely, to match and understand Russian fleet modernisation."
In a wide-ranging speech, Sir Stuart also described as "speculation" suggestions that the Royal Navy's amphibious landing capability, along with 1,000 Royal Marines, could be axed.