The Royal Navy's HMS Mersey has tracked a Russian submarine as it travelled through the North Sea and English Channel.
The Portsmouth-based patrol ship was on watch as the Kilo-class attack submarine, RFS Rostov Na Donu, made its journey from the Baltic to the Mediterranean.
HMS Mersey reported on the movements of the Russian Black Sea Fleet submarine so NATO allies could track her progress.
Commanding Officer of HMS Mersey, Lieutenant Commander Will Edwards-Bannon, said the ship and her crew "have conducted a particularly varied range of missions recently", culminating with the tracking of the RFS Rostov Na Donu.
HMS Mersey was also on duty when the Kilo-class submarine made the reverse journey in October last year, as it returned from operations in the Mediterranean back to the Baltic.
A Navy spokesman said: "This latest operation comes amid a busy time for the Royal Navy’s patrol ships, with Mersey and her sister ships HMS Tyne and HMS Severn all on maritime security patrols in the seas around the UK.
"Royal Navy patrol ships are involved in a range of missions, including fishery protection, which has been their responsibility for many years, but also coordinating with the Joint Maritime Security Centre to share information relating to suspicious or dangerous activity at sea alongside the Maritime and Coastguard Agency and National Crime Agency."
Cover image: RFS Rostov Na Donu whilst being tracked by HMS Mersey (Picture: Royal Navy).