Nuclear submarine in near-miss with ferry in Irish Sea
The submarine was at periscope depth when it came close to the Stena Superfast VII.
A nuclear-powered Royal Navy submarine has been involved in a near-miss with a ferry.
An investigation has been launched into the previously unreported incident, which occurred in the Irish Sea on November 6.
The submarine was submerged at the depth needed to extend its periscope above the surface of the water when it came close to the Stena Superfast VII, which operates between Scotland and Northern Ireland.
A Royal Navy spokesman would not confirm which of its ten submarines was involved. All ten are nuclear-powered, while four carry Trident nuclear missiles.
The ferry has a capacity for 1300 passengers and 660 cars.
A spokesman for the Marine Accident Investigation Branch (MAIB) said: "In November, we were notified of a close-quarters incident between the ro-ro (roll-on/roll-off) ferry Stena Superfast VII and a submarine operating at periscope depth.
"We have carried out a preliminary assessment of the evidence in this case and the Chief Inspector of Marine Accidents has decided to open a safety investigation.
"The investigation is being conducted with the full co-operation of the Royal Navy. A report will be published when our investigation has concluded."
A Navy spokesman said: "We can confirm the sighting of a Royal Navy submarine between Belfast and Stranraer on November 6 2018. We are co-operating with the MAIB's investigation."
A spokesman for Stena said: "Stena Line can confirm that on Tuesday November 6, 2018, Stena Superfast VII and a submerged submarine came into close proximity during a scheduled crossing between Cairnryan and Belfast.
"At no stage were the vessel, passengers or crew in any danger. The incident is now under investigation by the Marine Accident Investigation Branch and we will of course co-operate fully in this."