Mourners out to pay tribute to the late Queen were stunned to see French President Emmanuel Macron strolling along the River Thames in London.
In a lighter moment during the Queen's official mourning period, the VIP and his wife Brigitte, who had earlier been to see Her Majesty's lying in state, decided to go walkabout through the Sunday London sunshine - and social media loved it.
The president mingled with those gathered on the streets around parliament.
Dozens of people reacted on social media by posting pictures or footage of France's head of state out and about and others made up spoof posts, mocking Mr Macron.
The French leader had dropped his trademark blue suit, for a more sombre dark navy jacket, dark trousers and black trainers, for the stroll.
He had apparently decided to go "incognito" to gauge the mood of the British public.
But as they walked through central London, flanked by aides and security guards, they were anything but "incognito".
"Possibly the least incognito person I've ever seen," said a number of people on social media, including Alix Mortimer, who added: "As the saying goes, 'as much talent for disguise as a giraffe in dark glasses trying to get into a polar bears-only golf club'."
Video online shows passers-by spinning their heads to stare at the entourage, some recognising the figures, some not.
One person tweeted - under a photograph appearing to show the immaculately-dressed leader, complete with designer sunglasses - considering a reasonably-priced pastry: "Juste un petit voyage incognito à Greggs" - "Just a little incognito trip to Greggs"!
To which someone replied: "Je voudrais un steak bake."
The image was quickly debunked as a fake.
The French President and First Lady were due to join hundreds of other foreign dignitaries at a reception at Buckingham Palace on Sunday evening, where they planned to present King Charles with a book of pictures celebrating the Queen's historic links and visits to France over the years.