An unidentified Royal Navy submarine nearly collided with ro-ro ferry Stena Superfast VII in a close quarters incident in the Irish Sea which is currently under investigation.
The near-miss occurred on November 6 and the UK Marine Accident Investigation Branch (MAIB) on January 21 decided to open a safety investigation following a preliminary assessment of the evidence.
The submarine was at periscope depth at the time of the incident, it was noted.
A MAIB spokesperson said the Royal Navy was cooperating in the investigation adding that a follow-on report would be published once the investigation is completed.
The Royal Navy currently operates six nuclear-powered attack submarines and four ballistic-missile submarines.