The Guardian reported that Johnson asks Macron "Is that why he was late?" before Trudeau interjects "He was late because he takes a 40-minute press conference off the top."
Trudeau adds "Oh, yeah, yeah yeah..." he announced before he is cut off by Macron, who speaks animatedly to the group. Macron's back is to the camera and his words are inaudible.
Whom the group is talking about is not known, but it appears that the reference is to the US President, who is known for his long, rambling press conferences and who had an unscripted 50-minute back-and-forth with reporters on Tuesday, the report added.
The footage later shows an incredulous Trudeau telling the group, which also included Mark Rutte, Prime Minister of the Netherlands, and Princess Anne "You just watched his team's jaws drop to the floor."
It is again not known whom the group are talking about. The leaders also do not appear to realise that their conversation is being recorded.
Meanwhile, President Trump on Wednesday abruptly canceled a press conference scheduled to cap his contentious trip to England for the North Atlantic Treaty Organization's 70th anniversary meeting.
Trump tweeted on @realDonaldTrump ....When today's meetings are over, I will be heading back to Washington. We won't be doing a press conference at the close of NATO because we did so many over the past two days. Safe travels to all!"
The post got 13.8K responses with 7,500 people talking about it.
The presser was scheduled to come after his series of meetings with NATO members like German Chancellor Angela Merkel and Italian Prime Minister Giuseppe Conte.