Donald Trump stoked his simmering feud with The New York Times at the weekend, accusing the stately newspaper of inventing a source for a story. More fake news, was the gist.

Just one problem: The source was in fact a White House official who conducted a briefing for reporters on condition he not be named, according to both the newspaper and reporters who attended.

Such arrangements are commonplace, allowing aides to fill in details about complex issues without overshadowing the president’s own words on the subject.

It seems no-one told Mr Trump.

In a tweet, he accused the newspaper of quoting an official “who doesn’t exist” as he disputed a line about a possible summit with North Korea, which read: “a senior White House official told reporters that even if the meeting were reinstated, holding it on June 12 would be impossible, given the lack of time and the amount of planning needed.”