The UK has signed an international treaty with Japan and Italy to build the next generation of stealth fighter jet.
The deal will see the headquarters for the Global Combat Air Programme (GCAP), the defence partnership between the three nations, based in Britain.
Prime Minister Rishi Sunak announced the collaborative international effort to build military planes with supersonic capability and cutting-edge technology a year ago.
Called Tempest in the UK, the ambition is for them to take to the skies by 2035 and serve as a successor to the RAF Typhoon.
The Ministry of Defence (MOD) said the signing of the treaty in Tokyo on Thursday marked a “key stage” in the development of the aircraft.
Defence Secretary Grant Shapps was in the Japanese capital to sign the document alongside his Italian and Japanese counterparts, Guido Crosetto and Minoru Kihara.
He said: “Our world-leading combat aircraft programme aims to be crucial to global security and we continue to make hugely positive progress toward delivery of the new jets to our respective air forces in 2035.
“The UK-based headquarters will also see us make important decisions collaboratively and at pace, working with our close partners Italy and Japan, and our impressive defence industries, to deliver an outstanding aircraft.”
When complete, the Tempest will boast a powerful radar that can provide 10,000 times more data than current systems, the MOD said.
Pilots will be able to use virtual reality in the aircraft’s digital cockpit, with vital information displayed directly in front of them.
The on-board weapons system will deploy artificial intelligence and machine learning to “maximise the effect” its arsenal can deliver, the department said.
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Some £2bn has been committed to the project by the UK Government up to 2025, with the investment announced in 2021 before the partnership with the other two nations on GCAP was confirmed.
The MOD awarded the contract to BAE Systems, in collaboration with Leonardo UK, missile maker MBDA UK and Rolls-Royce, as well as industry partners from Japan and Italy.
Joint development of the aircraft is due to start in 2025.
The treaty confirms that the UK will host the joint GCAP government headquarters, with a Japanese chief executive at the helm at the outset.
Locations for the government HQ and a separate industry base, which will also be in the UK and led by an Italian, are to be announced in “due course”, the MOD said, along with a timeline for opening.
The department said the offices will support UK jobs and facilitate close working with Japanese and Italian colleagues.
The next step is for the treaty signed by the allies on Thursday to be sent to all three national parliaments for ratification.