A British Royal Navy submarine, armed with Trident nuclear missiles, faced a severe malfunction, forcing the vessel to approach its crush depth, according to UK media reports.

The Vanguard-class submarine, carrying 140 crew members, experienced a sudden failure in its depth gauge during a mission in the Atlantic Ocean. Engineers intervened urgently, preventing the submarine and its nuclear reactor from descending further just moments before a potential disaster, the UK-based Sun reported.

Submarine was near ‘crush depth’

While on patrol, the depth indicators ceased functioning, leading the crew to mistakenly believe the submarine was level when, in reality, it was diving deeper. Another gauge at the rear of the submarine revealed they were heading into the “danger zone,” prompting engineers to raise the alarm. The mistake reportedly led the submarine to approach its “crush depth,” also referred to as “collapse depth” in the US.

“It’s not the engineers’ job to control the sub’s depth but they saw how deep they were and realised something was wrong. Technically the sub was still at a depth where we know it can operate, but if it ever has to go that deep the whole crew is piped to action-stations. That hadn’t happened. The sub wasn’t supposed to be there, and it was still diving. And if it had carried on going, it doesn’t really bear thinking about,” an unnamed source told the UK newspaper.

Although the specific depth the submarine reached remains unknown, the maximum operational depth for this type of vessel is approximately 500 meters, according to multiple reports. British media reports said the incident triggered an immediate probe, assuring insiders that it did not impact the UK’s nuclear deterrent.

Vanguard-class nuclear-powered submarine

The involved Vanguard-class nuclear-powered ballistic missile submarine remains unidentified among the four vessels: HMS Vanguard, Vengeance, Victorious, and Vigilant. While each displaces 15,900 tonnes submerged and exceeds 149 meters in length, only two are presently operational, with one undergoing refitting and another undergoing sea trials.

Since 1969, at least one Royal Navy submarine with nuclear missiles has been on patrol to counter sudden attacks. Vanguard submarines possess the capability to house 192 nuclear warheads but are currently limited to a maximum of 48. In the wake of the incident, a Royal Navy spokesperson told Sun, “We do not comment on operations. Our submarines continue to be deployed globally, protecting national interests.”