British defence giant BAE Systems will complete construction of the Royal Navy's new submarine HMS Audacious in a deal worth £1.2 billion, the Ministry of Defence (MoD) announced.
The contract (equivalent to $1.9 billion, 1.5 billion euros) for Audacious, the fourth of seven Astute Class vessels being built for the Royal Navy, will secure 3,000 jobs at the company's shipyard in Barrow, northwest England.
The hunter-killer submarines will gradually replace the Trafalgar Class currently in operation.
The first two boats in the series, Astute and Ambush, have undergone sea trials and a third boat, Artful, is nearing completion at the Barrow plant.
Preliminary work has been undertaken on Anson, the fifth craft, while construction is yet to begin on boats six and seven.
Astute suffered serious problems during its trials, encountering flooding and electronic malfunctions which forced it to resurface.
Defence Secretary Philip Hammond said: "This contract marks an important step forward in the progress of our Attack Submarine programme and moves the Royal Navy closer to adding more of these highly-advanced and powerful attack submarines to its fleet.
The minister also pledged further funding for BAE to start work on the remaining boats.
"Our ability to commit an additional £1.5 billion for boats five, six and seven underlines the benefits of a balanced budget and fully-funded equipment programme that gives our Armed Forces greater certainty.
"This funding demonstrates our commitment not only to a key Royal Navy capability, but also to the submarine industry in Barrow, which will play a vital role in Britain's defence for decades to come."
The Astute class subs are each powered by a Rolls-Royce nuclear propulsion system which boast a reactor that never needs refuelling.
They are armed with both Tomahawk land attack missiles and Spearfish torpedoes, with a range of 1,200 miles (1,920 kilometres).