The writer is?a former British diplomat and author of ‘Hard Choices’

“France and the United Kingdom agree that there is no extreme threat to Europe that would not prompt a response by our two nations.” This sentence in the Northwood declaration issued by Prime Minister Sir Keir Starmer and President Emmanuel Macron at the UK-French summit last week signalled a potentially far-reaching shift in the defence priorities of both countries as they come to terms with Vladimir Putin’s aggression in Ukraine and Donald Trump’s unreliability as an ally.

The most productive UK-French summit since 2010 will be followed by the first visit of German Chancellor Friedrich Merz to London this week. There will be none of the pageantry and glitz of Macron’s state visit, but it will also be an important moment. Merz and Starmer will sign a wide-ranging treaty of co-operation, strengthening what has been the weakest leg of the London-Paris-Berlin triangle as the three countries take on more responsibility for European security. These agreements turn the page on a decade in which Brexit overshadowed relations between the UK and its neighbours.