For decades Nato’s guiding philosophy has been “One for all, all for one.” Article 5 of the North Atlantic Treaty requires Nato members to defend an ally which has been attacked with armed force if necessary. Today that principle was turned on its head. It wasn’t an attack on one ally that has prompted a collective defence from Nato members, but an attack by one of the 29: France’s President, Emmanuel Macron.

The French president’s recent controversial comments that Nato is “brain dead” and that Russia should be brought in from the cold made for a tetchy start to the alliance’s 70th anniversary celebrations in London yesterday, and a massive headache for tomorrow’s leader’s meeting in a Hertfordshire hotel.

More controversially, Macron has raised the question of what is the purpose of Nato and which enemy is the alliance meant to contain? Is  it Russia? Or China? Or maybe, as he states it should be, Islamic terrorism.