The UK government has to be satisfied, but all indications suggest the state visit will begin as planned on Monday, possibly with some minor adjustments to more public-facing events.

Donald Trump also seems to expect the trip to go ahead, telling Fox News: "King Charles is coming, and he's a great guy."

Buckingham Palace said the King was "greatly relieved" to hear that the US president, Melania Trump and other guests at the White House Correspondents' Dinner had been unharmed.

It's understood that the King and Queen privately reached out to the Trumps to express their sympathies for those caught up in the attack.