The head of the Royal Navy has warned that Russia is “probing us for weakness” and that Britain is facing maritime threats on a scale not seen since the Cold War.
First Sea Lord General Sir Gwyn Jenkins said Russia was “probing, testing and mapping” around critical undersea infrastructure as he called for the Royal Navy to strengthen its warfighting readiness and develop a larger hybrid fleet combining conventional warships with autonomous and uncrewed systems.
Speaking in Whitehall on Wednesday, Jenkins described Russia as the greatest current threat to UK security and highlighted its advanced submarines, long-range precision weapons and specialist deep-water capabilities.
Russia 'probing us for weakness'
Jenkins said: “The greatest threat to our security today is Russia.”
He said Russia retained increasingly difficult-to-track submarines, long-range precision weapons and specialist systems capable of operating deep underwater.
Jenkins added: “Russia is probing, testing and mapping. It seeks advantage in the grey zone, particularly around the critical undersea infrastructure on which modern societies rely.”
He said Russia regards Britain as one of its principal adversaries among Ukraine's Western supporters and added: “We know that Russia is probing us for weakness. And we are facing threats in a way we have not been since the Cold War.”
Concern over Britain's undersea infrastructure
The warning focuses heavily on the network of cables, pipelines and other infrastructure running beneath the sea that modern communications, energy supplies and the wider economy depend upon.
Jenkins said such infrastructure is difficult to monitor and can be difficult to repair rapidly if damaged.
The concerns are not new. The Ministry of Defence and Royal Navy have repeatedly warned about increased Russian activity around the UK and North Atlantic.
Official figures released in August showed Royal Navy maritime operations to monitor Russian activity increased by 25% during the first seven months of 2026 compared with the same period in 2025.
Warships and helicopters spent 21 days monitoring Russian activity in UK waters and the North Atlantic during July alone.
Royal Navy has previously warned of Russian seabed activity
In April, the Royal Navy said Russian interference with shipping and probing of critical national infrastructure required Britain and its northern European allies to strengthen their collective naval response.
The Ministry of Defence has also developed the Atlantic Bastion programme in response to increased Russian submarine and underwater activity.
That programme is intended to combine ships, submarines, aircraft, autonomous vessels and AI-powered acoustic detection technology to strengthen Britain's ability to detect and track potential underwater threats.
The Royal Navy said when announcing the programme that UK Defence Intelligence had identified Russian efforts to modernise capabilities capable of targeting critical undersea cables and pipelines.
Jenkins calls for stronger 'hybrid Navy'
The First Sea Lord used his latest speech to argue that Britain needs a larger and more lethal Navy, increasingly combining crewed warships with drones and other autonomous systems.
He said Britain's dependence on the Atlantic meant maritime security remained fundamental to national security and argued that the country must rediscover what it means to be a maritime nation.
Jenkins said: “If we are to prevail in the Atlantic again, we must strengthen our warfighting readiness and rediscover what it means to be a maritime nation.”
The Royal Navy has already adopted the concept of a “Hybrid Navy”, combining conventional and nuclear capabilities with autonomous and uncrewed technology.
Warning is military assessment, not announcement of new Russian attack
Jenkins's comments represent the professional assessment of the First Sea Lord rather than confirmation that Russia has launched a new attack against British infrastructure.
However, his warning comes against a documented increase in Royal Navy deployments to monitor Russian vessels and longstanding official concern over Russian activity in the North Atlantic and around critical undersea infrastructure.
The First Sea Lord is the professional head of the Royal Navy and advises the Chief of the Defence Staff and Defence Secretary on maritime strategy and policy.