The company is building a total of seven Astute-class boats for the service.
In December last year, the fifth Astute-class nuclear submarine was named Anson in a virtual ceremony.
The 97m-long, 7,400t submarine will now move forward with the next phase of its test and commissioning programme. It will leave for sea trials in 2022.
The Astute-class boats are capable of ‘circumnavigating the globe submerged, producing their own oxygen and drinking water’.
All these boats feature advanced nuclear technology and never require to be refuelled.
More than 10,000 people work on the Dreadnought and Astute programmes at BAE’s Barrow site.
BAE expects to hire 200 graduates and 1,500 apprentices over the next five years.
The first four vessels, namely HMS Astute, HMS Ambush, HMS Artful and HMS Audacious, are already in service.
Along with Anson, the final two submarines, namely Agamemnon and Agincourt, are at various stages of construction.
BAE Systems Submarines managing director Steve Timms said: “The launch marks an important milestone in the Astute programme and seeing Anson enter the water at such an advanced state is a tangible demonstration of everyone’s hard work over the years.
“Designing and building nuclear-powered submarines is a national endeavour and days like this bring a huge sense of pride for our workforce, our partners in the submarine enterprise and our UK supply chain, not to mention our communities.
“We now look forward to a successful test and commissioning phase and working alongside Anson’s crew to prepare the submarine for operations with the Royal Navy.”
In February last year, Thales UK secured a £330m contract from BAE Systems Submarines to work on the Royal Navy’s Dreadnought-class submarines.