French and British troops swapped roles to take part in the changing of the guards ceremonies outside the palaces of the other country's head of state, in an unprecedented move to celebrate 120 years since the Entente Cordiale.
Signed in 1904, the Entente Cordiale accord cemented an improvement in relations after the Napoleonic Wars and is seen as the foundation of the two NATO members' alliance to this day.
The ceremonies saw British guards take part in the changing of the guard outside the Elysee Palace of President Emmanuel Macron, while his French guards did the same outside Buckingham Palace in London of King Charles.
At the Elysee, 16 members of the Number 7 Company Coldstream Guards of the UK embassy, wearing their traditional bearskin hats, relieved French counterparts from the first infantry regiment this morning.
The French army choir sang the two national anthems - God Save the King and La Marseillaise.
"This is the first time in the history of the Elysee that foreign troops have been invited to participate in this military ritual," a French presidential official said.
Later in London, the Duke and Duchess of Edinburgh inspected UK and French troops on Buckingham Palace's forecourt.
Prince Edward and his wife Sophie, representing King Charles who is continuing his cancer treatment and was not at Buckingham Palace, walked past 32 members of the 1st and 2nd Infantry regiments of the Garde Republicaine and then 40 guardsmen from F Company Scots Guards, lined up opposite their French counterparts.
At the end of 2023, Mr Macron made the changing of the Republican Guard public again, on the first Tuesday of each month, though the ceremony is much less spectacular than its counterpart outside Buckingham Palace.
Two sections of the 1st and 2nd Infantry Regiment of France's Republican Guard participated in the London.
The event on the forecourt of Buckingham Palace marked the first time a country from outside the Commonwealth - which mostly includes English-speaking former British colonies and possessions - has taken part in the changing of the guard.
The signing of the Entente Cordiale on 8 April 1904, is widely seen as preparing the way for France and Britain joining forces against Germany in World War I.
While the accord is often used as shorthand to describe the Franco-British relationship, ties have been bedevilled by tensions in recent years particularly after Brexit.
Migration has been a particular sticking point, with London pressuring Paris to halt the flow of migrants across the Channel.
But a state visit by King Charles last autumn - one of his last big foreign engagements before his cancer diagnosis - was widely seen as a resounding success that showed the fundamental strength of the relationship.
"This anniversary is therefore an opportunity to promote the historic military, diplomatic, economic and cultural ties that unite France and the United Kingdom and to reaffirm our common values," the French presidential official said.
