The huge cash boost will pay for a ‘space command’ capable of launching the UK’s first rocket by 2022 and the creation of an agency dedicated to artificial intelligence.

The money will be spread over four years and create 10,000 new jobs in Britain.

‘I have taken this decision in the teeth of the pandemic because the defence of the realm must come first,’ the Prime Minister said in a statement ahead of the announcement.

‘The international situation is more perilous and more intensely competitive than at any time since the Cold War and Britain must be true to our history and stand alongside our allies. To achieve this we need to upgrade our capabilities across the board.

‘This is our chance to end the era of retreat, transform our armed forces, bolster our global influence, unite and level up our country, pioneer new technology and defend our people and way of life.’

The move will come as a relief for military chiefs who have been pressing for a multi-year settlement to enable them to plan effectively for the future.

It is thought their demands were being resisted by the Treasury, with Chancellor Rishi Sunak holding out for a one-year deal – along with the rest of Whitehall – in next week’s spending review.

The sum is not enough to fill the military’s budget gap but is far above the Government’s manifesto commitment to a 0.5% real terms increase for each year of the Parliament.

Mr Johnson is due to unveil the plan in the House of Commons on Thursday, where he is expected to tell MPs that the move will generate jobs and demonstrate to allies like the US that the UK is a reliable partner.

Officials said the investment would cement the UK’s position as the largest defence spender in Europe and the second largest in NATO.

As well as promising a new space command, the Prime Minister will also set out plans for a national cyber force to protect the country from attack.

The money will be underpinned by of an additional £1.5 billion investment in military research and development with a commitment to invest further in the Future Combat Air System to develop the next generation of fighters for the RAF.

Defence Secretary Ben Wallace said: ‘This is excellent news for defence, and provides us with the financial certainty we need to modernise, plan for the future and adapt to the threats we face.

‘It demonstrates the Prime Minister’s recognition of how important defence is to our resilience and to the reputation of the United Kingdom.

‘This settlement secures UK jobs and livelihoods, allows us to invest in our fantastic shipyards and aerospace industry, spreading prosperity to every corner of the UK.

‘Next year represents a huge opportunity for this country, and defence will be at the forefront of creating the jobs and business opportunities that will help us build back from the pandemic.’