The Prince of Wales has met US President-elect Donald Trump while visiting France for the ceremonial reopening of Notre-Dame cathedral.
Prince William joined other world leaders in Paris to mark the restoration of the world-famous landmark, which was devastated by a fire five years ago.
He is set to have a meeting with president-elect after the ceremony, Kensington Palace said.
During the event, French President Emmanuel Macron delivered a speech in which he said of the restoration: "we must treasure this lesson of fragility, humility and will".
Other leaders and dignitaries at the event included Ukrainian President Volodymyr Zelensky and outgoing US first lady Dr Jill Biden, who was representing President Joe Biden.
It is expected that the prince will discuss the importance of the US-UK "special relationship" with both Trump and the first lady during their respective meetings.
Greeting the prince at the ceremony, Trump gave William a pat on the shoulder before the two shook hands and spoke for a few seconds.
He last met Trump in 2019 when the then-president made a state visit to the UK.
Prince William, who is attending at the request of the UK government, joined French President Emmanuel Macron and dozens of other heads of state at the ceremony on Saturday.
William and Trump, who will speak at another location in Paris after the ceremony, had originally been scheduled to meet before the event.
The prince had also been due to meet Dr Biden ahead of the ceremony but will now meet her at the ceremony.
Kensington Palace said he had been delayed by weather on his journey from the UK to France.
The Archbishop of Paris Laurent Ulrich led more than 1,500 guests through the reopening service.
A choir sang out as Macron took his seat next to Trump. A message from the Pope was read aloud before the French president delivered his address.
Parts of the event also had to be reconfigured due to the stormy weather - with a concert that was due to take place on the esplanade actually being staged on Friday.
The prince's last official trip to Paris was in 2017, when he visited with the Princess of Wales for a two-day trip in the aftermath of the Brexit result.
He joined other world leaders in Normandy earlier this year for the 80th anniversary commemorations of the Second World War D-Day landings.
The medieval cathedral has been closed since a major fire tore through it in 2019, destroying its stained-glass windows and wooden interiors before toppling its spire.
Some 600 firefighters battled the blaze for 15 hours. The main structure of the 850-year-old building was saved, including its two bell towers.
Macron set a five-year goal for the reconstruction of the Catholic church shortly after the fire.
An estimated 2,000 masons, carpenters, restorers, roofers, foundry-workers, art experts, sculptors and engineers worked on the project, which reportedly cost €700m (£582m).
Tickets for the first week of Masses in the cathedral sold out in 25 minutes, the cathedral's rector said.
Royal charm offensive to help build bridges
Analysis by Sean Coughlan, royal correspondent
Prince William has been scrambled, like in his old air ambulance days, to rush to this meeting in Paris with President-elect Donald Trump.
Although what's in need of rescue on this occasion is the well-being of the special relationship between the US and the UK.
It's an important connection for both sides - and for wider military links such as Nato - but there's not a lot of obvious empathy between Starmer's Labour government and the incoming Republicans.
So the royals, who are funded by taxpayers, are being deployed to smooth the path, with Prince William taking on the statesman role, meeting Trump before attending the reopening of the Notre Dame cathedral.
Trump is a royal fan, so that might make for a more positive connection. Prince William last met Trump in 2019, during the then-president's visit to the UK, where Trump spoke very enthusiastically about his meeting with the late Queen Elizabeth II.
But there's a massive contrast in their styles. Prince William's flagship project is his Earthshot environmental awards, while Trump has dismissed efforts to boost green energy as a "scam".
This week Prince William went to serve dinner at the Passage homelessness charity and on Friday night he was helping with a "kindness tree" outside Westminster Abbey.
A kindness tree and campaigning on housing and climate-change aren't exactly the 'Make America Great Again' style.
But the aim of this hurriedly-arranged meeting will be for a royal charm offensive to help build bridges at an uncertain time for western alliances.