NATO The North Atlantic Treaty Organization aka Intergovernmental military alliance

The North Atlantic Treaty Organization, also called the North Atlantic Alliance, is an intergovernmental military alliance between 29 North American and European countries. The organization implements the North Atlantic Treaty that was signed on 4 April 1949. Wikipedia

• Nato is the world's most powerful defence alliance
• It was set up in 1949, after World War Two, amid anxiety over Soviet expansion
• It was founded on the principle of collective defence between allies

The prime minister arrived at the Nato leaders meeting in Watford earlier this morning, which marks the 70th anniversary of the alliance.

Speaking on the way in, Prime Minister Boris Johnson said Nato continued to provide "peace and prosperity for hundreds of millions of people" because of "a very simple concept of safety in numbers."

"At the heart of it is a pledge that we will come to one another's defence - all for one and one for all."

But Mr Johnson warned Nato "cannot be complacent". He said the UK would continue to invest 2% of its GDP in defence and its commitment to the alliance was "absolutely rock solid".

Footage showed Mr Trudeau, UK PM Boris Johnson and French leader Emmanuel Macron discussing an impromptu press conference held by Mr Trump.

Despite the divisions, Mr Johnson - the host of the event - described Nato as a "giant shield of solidarity" that "protects nearly a billion people", saying at the start of the meeting at a luxury resort in Watford: "As long as we stand together, no-one can hope to defeat us."