A Royal Navy submarine and a car ferry reportedly came dangerously close to colliding late last year.
The incident took place on November 6, 2018, in the Irish Sea between England and Ireland. The U.K. has not commented on what type of submarine was involved, but its navy operates four ballistic missile submarines armed with nuclear weapons. Royal Navy submarines have been involved in several incidents with other vessels in the past decade, including a rare collision with another submarine.
The car ferry was the boat involved in the “close quarters incident” with the as-yet-unnamed sub, which was at periscope depth. A ro-ro (roll on, roll off) ferry, the Stena Superfast VII travels between Northern Ireland and Scotland. It has room for 1,300 passengers and 660 cars. The U.K.’s Marine Accident Investigation Branch has opened an investigation into the incident and says the Royal Navy is cooperating fully.
The Royal Navy operates 11 submarines, all nuclear powered. Seven of the submarines are attack submarines of the Astute and Trafalgar classes. Neither class of ships typically carries nuclear weapons. The remaining four RN submarines are ballistic missile submarines of the Vanguard class (see above). Under a policy known as Continuous at Sea Deterrent, at least one Vanguard is on patrol at any one time, carrying 16 Trident D-5 ballistic missiles. According to the Federation of American Scientists, each D-5 in turn carries three nuclear warheads, for a total of 48 nuclear weapons per ship. The Vanguard class is also based at Faslane, Scotland, which has access to the Irish Sea.
U.K. submarines have been involved in several collisions in the past ten years. In April 2015, a submerged submarine in the nets of a Northern Ireland–based fishing trawler, nearly dragging the tiny boat underwater before the crew cut the nets. In 2016, the submarine HMS Ambush off the coast of Gibraltar, resulting in minor damage to the sub. In 2009, the U.K. ballistic missile submarine HMS Vanguard with one of its French counterparts, Le Triomphant, in the Atlantic.