The 97-metre-long submarine weighing 7,400 tons can manufacture its own oxygen and fresh water from the ocean and circumnavigate the globe without surfacing.
The Astute-class submarines carry Tomahawk Land Attack Cruise Missiles and Spearfish heavyweight torpedoes.
It was the sixth of seven nuclear-powered Royal Navy submarines to be launched from the site.
The first five submarines, HMS Astute, HMS Ambush, HMS Artful, HMS Audacious and HMS Anson, have been handed over to the Royal Navy.
In April, during Agamemnon’s naming ceremony, Steve Timms, managing director at BAE Systems’ submarines business, said: “This is a key milestone for Agamemnon and the UK nuclear submarine programme, and contributes to the Government’s defence nuclear enterprise command paper, which underpinned the importance of our business and Barrow in delivering this national endeavour.”