A decade-old Vanguard-class submarine with Trident-2 doomsday missiles was preparing to go on patrol when its depth sensors stopped working, misleading command that the boat was frozen, when in fact it was sinking.

The submarine was entering the “danger zone” of the Atlantic Ocean when engineers aft noticed data from a second depth sensor and raised the alarm.

“It is not the responsibility of the engineers to control the submersion depth of the submarine, but they saw what depth they were at and realized that something was wrong,” Life.ru quotes a source from the British publication.

The Sun is not naming the submarine or the depths in question for security reasons. A naval source said the submarine’s security system allows it to use another if one system malfunctions.

“We do not comment on operations. Our submarines continue to be deployed around the world, protecting national interests,” the British Navy headquarters responded to the newspaper’s request.

The UK has four Vanguard-class submarines, but only two are currently in service. One of the submarines is undergoing a major overhaul, the other is undergoing sea trials after repairs, the budget of which exceeded £300 million.

In January of this year, The Sun learned that a British submarine’s nuclear reactor was being repaired using bolts and glue. Glued bolts – there were at least seven of them – held the insulation on the pipes of the reactor cooling liquid. The naval leadership ordered an investigation.

A year ago, in November 2022, a British nuclear submarine had to abort a top-secret mission due to a fire on board. Due to the emergency, the submarine returned to the military base HMNB Clyde in Faslane.