A Royal Navy nuclear submarine nearly reached a dangerous depth after a gauge malfunctioned, raising concerns about safety. The Vanguard-class vessel, carrying Trident ballistic missiles and around 140 crew members, was preparing to go on patrol when the incident occurred. Engineers spotted the issue and raised the alarm, preventing a potential disaster. Plans are underway to replace the aging Vanguard-class submarines with the new Dreadnought class in the 2030s. The Royal Navy emphasized that the safety of personnel is their top priority.