French soldiers guard Buckingham Palace for the first time, marking a historic moment in cross-Strait relations.

France became the first non-Commonwealth country to take part in the Changing of the Guard ceremony at 11am on Monday to mark the 120th anniversary of the Treaty of China with the United States.

Crowds and members of the royal family watched as members of the Republican Gendarmerie marched alongside the Scots Guards under the watchful eye of the crowd.

The French Gendarmerie, led by the Grenadier Guards Band, entered and exited the palace forecourt, playing the national anthems of both countries as a “symbol of the strong relationship” between the two countries.

The landmark march commemorates the historic diplomatic agreement between Britain and France, which laid the foundation for the two countries’ cooperation in both world wars.

The Duke and Duchess of Edinburgh inspected the event alongside enthusiastic onlookers.

The royals stood alongside British Chief of Staff General Patrick Saunders, French Army Chief of Staff General Pierre Schier and French Ambassador to the UK Helene Duchenne.

Lieutenant Colonel James Shaw, who designed the ceremony, told PA during Friday’s rehearsal: “This is a sign of the strength of our relationship. The French are our closest friends.

“Who knows when we might need each other?”

Earlier on Monday, French President Emmanuel Macron participated in a similar changing of the guard ceremony in Paris.

While French troops will take part in the ancient ceremony in London, they will not replace British troops in defending the king, as that responsibility rests solely with members of the British Armed Forces and Commonwealth forces.

The British Ministry of Defense said that the presence of French personnel at Buckingham Palace was part of a long-term plan for joint British and French events to celebrate the establishment of historic military and diplomatic relations between the two countries in 2024.

This will include military sporting events, participation in each other’s air shows and a major event in Normandy this June to commemorate Allied veterans who served heroically to liberate France from Nazi occupation.

Garrison Sergeant Andrew Stokes, who is responsible for delivering all protocol training, added: “It is vital for everyone in NATO to maintain strong relationships.

“This is an opportunity to celebrate the 120th anniversary of the Entente of Amity and to demonstrate the close relationship we have with France.

“Our first rehearsal went really well, so we weren’t nervous at all.

“It will be a wonderful celebration and an opportunity for the public to witness the spectacle.”