The Times reported the information.Admiral Sir Gwyn Jenkins, the First Sea Lord, issued the urgent warning during remarks at the International Sea Power Conference in London, highlighting what he described as unprecedented Russian investment in naval capabilities and increasingly aggressive underwater operations that threaten British interests."The advantage that we have enjoyed in the Atlantic since the end of the Cold War, the Second World War, is at risk. We are holding on, but not by much," Jenkins told the conference. "There is no room for complacency. Our would-be opponents are investing billions. We have to step up or we will lose that advantage. We cannot let that happen."The admiral's comments underscore growing concerns within British defense circles about Russia's expanding maritime presence, particularly its northern fleet operations. According to Jenkins, Moscow has poured billions into modernizing its naval forces "despite the millions of lives and the cost of their egregious illegal invasion of Ukraine."British waters have witnessed a 30 percent surge in Russian incursions over the past two years, including the appearance of spy vessels like the Yantar, suspected of surveilling undersea infrastructure. The ship entered UK territorial waters last month and reportedly directed laser beams at British military pilots.But Jenkins emphasized that visible surface operations represent only a fraction of the threat. "It's what's going on under the waves that most concerns me," he said, describing hostile submarine activity as his primary worry.The Royal Navy is responding with technological upgrades, including autonomous underwater gliders designed to detect enemy submarines and a planned Atlantic Bastion network of sensors to monitor maritime approaches. Contracts for the sensor system are expected next year.Jenkins, who took command of the service in May, inherits a navy facing significant operational challenges. The fleet has struggled with vessel availability, with aging Vanguard-class nuclear submarines forced into extended deployments due to maintenance backlogs. None of the navy's five Astute-class attack submarines are currently believed to be operational due to refits and technical issues.Recruitment difficulties have also plagued the service, though officials say conditions are gradually improving.On Monday, Jenkins announced a comprehensive overhaul of officer training following several high-profile scandals. "We need war-fighting leaders, which is why we've embarked on a programme to revise the way we train our officers within the Royal Navy and the Royal Marines," he said. "We need leadership excellence. That is, leaders who can deliver results."His predecessor, Sir Ben Key, became the first navy chief to have his service terminated after an investigation found his conduct had violated service standards amid allegations of an inappropriate relationship with a subordinate. Several other commanding officers have faced disciplinary action in recent months.Jenkins stressed that maintaining Atlantic security would require both rapid modernization and continued cooperation with NATO allies, warning that Britain cannot afford to lose its maritime edge as geopolitical tensions escalate.