UK Defence Secretary Michael Fallon has announced an investment of £642m for the Royal Navy's future nuclear deterrent Successor submarine programme.
The Successor submarines will replace the navy's existing fleet of four Trident missile Vanguard-class nuclear submarines from the 2030s, and are being designed to be some of the stealthiest vessels in the world.
Fallon said: "Our nuclear deterrent provides the ultimate guarantee of our security and our way of life. That's why we are getting on with this investment.
"This money will support further design work, new infrastructure and the purchase of key parts such as engines and gearboxes, as well as jobs across the UK."
The investment, which takes the total cost of the Successor programme's assessment phase to £3.9bn, is aimed at furthering design work towards acquiring new parts and facilities.
Of the latest funding, £200m will be used to procure equipment such as power plants, including long lead items for the submarines, while significant investment will be made in UK / US collaboration for the Common Missile Compartment (CMC) programme.
Around £225m will be spent on new facilities at BAE Systems at Barrow-in-Furness, where the submarines will be assembled.
This investment aims to ensure submarines are built with maximum efficiency.
The CMC programme envisages the use of common missile compartment, which is the middle section of the boat with the submarine-launched ballistic missiles (SLBM) launch tubes, in the the US and UK's Trident replacement submarines.
Last month, the UK Government announced an investment of £201m to BAE systems to develop the design of the submarine, including designing the layout of the new vessel's equipment and systems, planning the manufacturing process, and producing early prototypes.
BAE systems is also constructing seven Astute-class nuclear attack submarines for the UK Royal Navy.
Image: An artist's impression of the Successor submarine. Photo: courtesy of Crown copyright.