Britain's civilian ships could be fitted with experimental new sensors to reveal Russian submarines in the Channel, The Telegraph can disclose.
Fibre-optic cables carrying a series of underwater acoustic receivers are already being used by the Dutch military and they have been tested by the Royal Navy.
Touted as the first of its kind in the world, the Dutch military says it has a "higher sensitivity than traditional arrays" and can spot targets more than 60 miles away.
The OptiArray system, built by Dutch technology firm Optics11, uses a large spool of cable that can be unwound behind a ship to detect the tell-tale sounds of submarines and warships at sea.
Traditionally, such technology has been reserved for specialist submarine-hunting warships, such as the UK's Type 23 frigates.
But Paul Heiden, Optics11's chief executive, said the system could be contained in a portable 10ft-long box and fitted to warships of any size, giving them an "unparalleled" ability to hunt submarines.
"Every ship, literally every ship, is capable of placing and running sea containers on their decks. That's exactly what we do here," the 59-year-old former Dutch marine said.
Speaking to The Telegraph from his office in Amsterdam, Mr Heiden said the system could also be fitted to civilian cargo ships to bolster Britain's defences, amid fears the country could be drawn into a war with Russia by 2030.
He added: "Just imagine you equip every civilian ship with a towed array. It won't use energy or cost anything … This is anti-submarine warfare in a box."
Towed arrays have been used for decades and offer a major advantage compared with hull-mounted systems, which sit close to machinery and propellers that can make it hard to detect faint sounds.
Optic11's towed array sensor cable can be deployed from any warship or civilian vessel - Dutch Military Defence/Sjoerd Hilckmann
Current systems are electronic, meaning they emit a faint electromagnetic field that could theoretically be detected. Mr Heiden said his fibre-optic system, which passes a beam of light through its sensors, emits no detectable signal.
The systems can also be deployed from land and run on the sea floor to protect critical underwater cables.
"We are selling an unfair advantage," he said. "We can pick up an oil tanker at 100km (62miles) and a frigate at about 50km. Particular unmanned surface vessels have a high motor sound. We can quickly pick that up in the tens of kilometres. That's really different from anything provided currently."
The Navy is under intense pressure to defend against Russian warships and submarines, which have stepped up their activity around the UK by a third in the past year.
A key area for surveillance is the vast gap between Norway and Greenland. The expanse is the gateway to Europe and the Atlantic for submarines of Russia's northern fleet.
Patrolling it is a significant task for the Navy, which has witnessed its surface fleet shrink to its smallest size in living memory.
Towards the end of the Cold War, the UK had 50 frigates and destroyers at its disposal along with about 30 submarines. Today, there are six destroyers and five frigates alongside six Astute-class submarines and four Vanguard boats carrying nuclear weapons.
At the same time, Russian warships are increasingly sailing through the Channel to guard sanctioned tankers of Vladimir Putin's shadow fleet illegally ferrying oil across the globe.
It has piled additional pressure on the Navy, which in July spent 21 days monitoring Russian naval activity.
The need for better technology to monitor submarines intensified this week after the Kremlin unleashed its latest underwater weapon.
Moscow's first Khabarovsk nuclear-powered submarine departed for sea trials in the White Sea.
The 443ft boat is the newest in Vladimir Putin's fleet and is designed to carry Russia's latest weapon of mass destruction, the Poseidon autonomous nuclear torpedo.
The Poseidon "Doomsday" weapon is intended to devastate coastal cities by creating radioactive tsunamis. Powered by a nuclear reactor, it theoretically has unlimited range, putting every coastal city in Nato within reach. It can also travel at speeds of up to 80mph.
The Khabarovsk nuclear submarine is undergoing sea trials - Russian Defence Ministry Press Service
The torpedo can carry a two-megaton nuclear warhead – more than 100 times more powerful than the atomic bomb dropped on Hiroshima in 1945. The Khabarovsk is reportedly configured to carry six Poseidons.
Russia's navy appeared to further intensify operations around Europe this week. Admiral Levchenko, a destroyer, escorted a sanctioned cargo ship and oil tanker through the Baltics to Egypt. The vessels are expected to pass through the Channel this weekend.
Moscow also prompted alarm after it deployed the Admiral Kasatonov, a frigate equipped with nuclear-capable Zircon hypersonic missiles, close to the German island of Fehmarn.
British naval sources brushed off the ship's deployment, claiming it was "routine". However, the action is part of a wider campaign that defence analysts are growing increasingly concerned about.
"We are seeing a real uptick in activity; a Russian warship stationed almost permanently in the Channel firing guns; (Dmitry) Medvedev (deputy chairman of Russia's security council) saying we will seize ships – this graph is going in the wrong direction," said Matthew Savill, director of military sciences at the Royal United Services Institute, a London think-tank.
The Royal Navy shadows the Russian frigate Neustrashimy in the English Channel in September 2025 - MoD/Reuters
Russia has also been accused of deploying submarines, spy ships and vessels from its shadow fleet to locate Britain's network of subsea fibre-optic cables which carry more than 99 per cent of international data traffic.
Sabotaging such systems could cause chaos and temporarily cripple the UK's economy, making the fibre-optic arrays vital for defence.
Britain is spending £1.5bn to develop a hybrid navy fleet, made up of various drone ships including some that can carry missiles and others built with sophisticated sensors.
Eight new Type 26 submarine-hunting frigates and at least five Type 31 frigates are also being built. Billions of pounds are also being invested in two new classes of submarines, including the UK's new fleet of Dreadnought nuclear deterrent boats and 12 hunter-killer submarines.
As part of the defence investment plan, the Government has committed £330m over four years to protect critical underwater infrastructure, including subsea cables and energy pipelines.
A Ministry of Defence spokesman added: "In the face of growing Russian threats, our Royal Navy warships and helicopters continue to monitor and deter Russian activity in UK waters."
The Dutch ministry of defence said it was "collaborating closely" with Optics11 to develop the new technology which would offer "higher sensitivity than traditional arrays".
Hailing the technology as "potentially groundbreaking … in the field of underwater detection", a spokesman added: "We are monitoring this development and actively supporting Optics11, including by assisting with the execution of tests.
"The system can contribute to anti-submarine warfare and the monitoring of subsea infrastructure."
