Design work for the next-generation Royal Navy submarines is under way after Defence Secretary Ben Wallace announced an investment of £170m.
The funding comes in the form of two £85m contracts, awarded to BAE Systems and Rolls-Royce, to deliver design and concept work for a future class of Navy submarine.
Over the next three years, the contracts' design work will help inform any future decisions defining the replacement for the Astute-class submarines.
Ian Booth, Submarine Delivery Agency CEO, said "designing and building submarines is one of the most complex and challenging" for maritime engineers.
"It is essential that work on the next generation underwater capability commences as early as possible," he said.
Watch: HMS Anson, part of the Astute-class, was rolled out of the factory earlier this year.
"This relies on some of the nation's most experienced defence nuclear experts from the very beginning of the design phase."
Industry teams, including Babcock International, are working with the Ministry of Defence (MOD) to progress design work on a range of options for a new, crewed, nuclear powered submarine – known as the Submersible Ship Nuclear Replacement (SSNR).
Mr Wallace said the investment marked "the start of a new journey for the Royal Navy's submarines".
"British designers and engineers will lead the way in developing submarines for our Royal Navy," he said.
"This multimillion-pound investment ensures that this vital capability will be ready to replace our Astute Class submarines as they come out of service."
The contracts will sustain about 250 roles with BAE Systems in Barrow and a further 100 jobs at Rolls-Royce in Derby.