The Astute class submarines are the biggest and most advanced attack submarines ever constructed for the Royal Navy.
Measuring 97m long, the submarines come with a number of technological firsts, the Astute-class submarines are the quietest class ever made.
They are also the first Royal Navy submarine to be fitted without optical periscopes – using high-specification video technology instead.
They are capable of hitting targets 1,000km from the coast and, as well as coming equipped with world-leading sensors, the submarines carry Tomahawk Land Attack Cruise Missiles (TLAM) and Spearfish heavyweight torpedoes.
The Astute-class submarines are able to circumnavigate the globe submerged and can produce their own oxygen and drinking water.
Only the amount of food that can be carried and the endurance of the crew limit the submarine's 90-day dived endurance.
A further three boats, named HMS Anson, HMS Agamemnon and HMS Agincourt, will complete the class and are currently under construction in Barrow.
Watch: HMS Trenchant reaches the end of her service.
The new submarines will replace the Trafalgar-class attack submarine, which includes HMS Trenchant - Britain's oldest operational submarine.
Ryan Ramsey, a former Trafalgar Class Submarine Captain, served on HMS Trenchant and told Forces News "she was a great boat".
"The Trafalgar-class has been the backbone for the Submarine Service and the attack submarine community for a number of years," he said.
"It's incredible what [HMS Trenchant has] done and what she's given to the Submarine Service, the Royal Navy and the country."
In September 2020, the Duchess of Cornwall visited HM Naval Base Clyde to mark the 10th anniversary of HMS Astute's commissioning.
Camilla the Duchess of Cornwall, who is the Lady Sponsor of the Astute-class submarine, thanked personnel for their commitment and handed out awards to some of HMS Astute's crew during her visit.