Woodburn welcomed the promotion of former Defence Secretary John Healey to chancellor. Healey very publicly resigned from the post insisting that the extra money awarded to defence “falls well short of what is needed to protect the country”.

An additional £13.5bn was boosted to an extra £15bn after he resigned but that will only bring spending on defence to 2.68% of GDP by 2030 – well short of the 3% Healey said was required. A further massive increase in spending will be needed to hit the government goal of 3.5% by 2035.

Shares in defence companies – including BAE – rose on the news that Healey was moving into number 11 but Woodburn knows he will have other departments competing for cash.

“We have tremendous respect for John,” he said. “He understands what is needed and I think in that sense its very good he’s in the Treasury role.”

He recognised Healey would have a host of complicated national finances to tackle. “But the fact that he understands the requirements of defence we see as a very positive thing”, he said.

The UK’s armed forces have dwindled since the end of the cold war. In 1990 – the army had 153,000 regular soldiers. Today that number is just 74,000.

But it is debatable how many human soldiers you need these days and Woodburn said a new era of autonomous lethal weaponry was close at hand.

“We’re not far from that. While we follow rules of ‘man in the loop’ we know very well that our adversaries are not always doing that,” he said.