“There’s no question how strong our military ties are. There is no questioning the need for strong defence cooperation, everyone’s convinced of that on both sides of the channel.”

There are more serious problems in cooperation on equipment projects, and some question how much each country is prepared to depend on the other to defend vital national interests.

“WE PAY AND WE PLAY”

Since the Lancaster House defence cooperation treaties of 2010, Britain and France have joined forces to counter Islamists in Mali and helped topple Libya’s Muammar Gaddafi.

Last month pilots from each country flew the other’s new fighter jets for the first time, following a major joint naval exercise in October dubbed “Corsican Lion”, part of efforts to create a Combined Joint Expeditionary Force by 2016.

And in an unusual step that Arbuthnot labelled an “extreme courtesy”, France has invited Britain’s ambassador - along with a German diplomat - to help draft France’s next long-term military plan, the Livre Blanc.

U.N. Security Council members France and Britain together account for around half of European military spending, have armed forces of similar size and are unafraid to deploy troops - “We pay and we play”, in the words of one British official.

But for decades Britain closely allied its defence strategy to that of the United States, while France sought to develop independent military muscle, and in 1966 left U.S.-dominated NATO’s integrated military structure.