Submarine HMS Trenchant has returned home to Devonport after 140 days away on deployment.
The Trafalgar-class boat honed her warfighting skills with NATO allies, working with vessels from 13 nations.
She covered 18,000 nautical miles – the equivalent of sailing down the west coast of Africa, onto Australia, New Zealand and Japan.
The nuclear submarine initially headed north to take part in Exercise Dynamic Mongoose off the coast of Iceland, along with Royal Navy ships and vessels from the US, Canada, France, Norway and Germany.
The exercise tested the ability of NATO’s anti-submarine forces to deal with the latest underwater threats, with submarine crews having to evade sonars and sonobuoys dropped in the ocean.
HMS Trenchant’s Commanding Officer, Commander Stephen Brian, said: "This was a great opportunity to train and refine our warfighting skills with our NATO allies and demonstrate the potency of HMS Trenchant."
After Exercise Dynamic Mongoose, the submarine sailed south to take part in more exercises that included Royal Navy Type 23 frigates, Merlin helicopters and the RAF's P-8A Poseidon.
The biggest exercise was Joint Warrior, Europe’s largest bi-annual collaborative training exercise in which a number of NATO allies simulate escalating tensions off the coast of Scotland.
In total, Trenchant trained and interacted with 25 surface and sub-surface assets, made up of nine submarines and 16 surface ships from 13 nations across the globe, including France, Canada and Portugal.
The crew remained in sea watches, six hours on, six hours off, throughout their deployment, the Royal Navy said.
Cover image: Royal Navy.