Agamemnon, named after the ancient Greek king, is the sixth of seven Astute Class submarines to emerge from BAE’s shipyard at Barrow-in-Furness in Cumbria.

The nuclear-powered craft weighs 7,400 tonnes and is 97 metres long. Having entered the water for the first time, Agamemnon will now begin the next phase of its test and commissioning programme before leaving Barrow for sea trials with the Royal Navy.

The Astute Class boats are the largest and most advanced attack submarines ever built for the Royal Navy.

Equipped with state-of-the-art nuclear technology, they never need to be refuelled. As they manufacture their own oxygen and drinking water for 98 crew members, they are also able to circumnavigate the globe without surfacing.

Steve Timms, managing director of BAE Systems Submarines, said: “The design and build of a nuclear-powered submarine is incredibly complex and a truly national endeavour, and I pay tribute to the thousands of highly-skilled people who have helped get Agamemnon...