The Duke and Duchess of Edinburgh have stepped in for King Charles as they watch French soldiers guard Buckingham Palace for the first time in history to mark 120 years of friendly relations between the two countries. 

The royals are filling in for the King as he continues to step back from royal duties while undergoing treatment for cancer. 

The Entente Cordiale accord was signed in 1904 and cemented an improvement in relations after the Napoleonic Wars. It is seen as the foundation of the two NATO members' alliance. 

The Duke and Duchess of Edinburgh 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.

They were joined by General Sir Patrick Sanders, UK Chief of General Staff, the French Chief of the Army Staff General Pierre Schill and France's ambassador to the UK Helene Duchene.

The event was the first time a non-Commonwealth country has taken part in the Changing Of The Guard ceremony. 

The Duchess of Edinburgh and Prince Edward, the Duke of Edinburgh, are stepping in on behalf of King Charles today 

The Duchess of Edinburgh, on behalf of King Charles, at the Changing of the Guard at Buckingham Palace

The Duke of Edinburgh at the Changing of the Guard at Buckingham Palace today 

Members of the British Army's Scots Guards march past the Queen Victoria Memorial as they take part in a special Changing of the Guard ceremony outside Buckingham Palace

French soldiers are guarding Buckingham Palace for the first time in history to mark 120 years of friendly relations between the two countries

The Duchess of Edinburgh at the Changing of the Guard at Buckingham Palace

The Duchess of Edinburgh at the Changing of the Guards ceremony today 

France's Gendarmerie's Garde Republicaine arrive at Buckingham Palace to take part in the Changing of the Guard

The Duchess of Edinburgh smiled as she attended the ceremony today 

French President Emmanuel Macron shakes hands to onlookers outside the Elysee Palace in Paris

British soldiers enter the Elysee Palace today in Paris

French President Emmanuel Macron and British ambassador to France Menna Rawlings gesture outside the Elysee Palace in Paris today 

French President Emmanuel Macron shakes hands to onlookers outside the Elysee Palace today

Major Jamie Drummond-Moray, Officer Commanding F Company Scots Guards, said: 'It is an enormous privilege for us to host the French here in London and to play such a significant part in a ceremony that has never happened before with a non-Commonwealth country.

'It really is a monumental occasion and more so given that it is marking 120 years of the strong relationship between the UK with France.

'I think it's a great honour for all our soldiers, and a fantastic day for everyone in France and the UK.'

Meanwhile, the UK's Foreign Minister David Cameron and his French counterpart Stephane Sejourne celebrated their 'close friendship' in a joint op-ed published late on Sunday.

They said it was key at a time when NATO is mobilised to ensure Ukraine does not lose its fight to repel the Russian invasion.

'Britain and France, two founding members and Europe's nuclear powers, have a responsibility in driving the alliance to deal with the challenges before it,' the diplomats wrote in The Telegraph.

'We must do even more to ensure we defeat Russia. The world is watching - and will judge us if we fail.'

British troops and France's Gendarmerie's Garde Republicaine during the parade at Buckingham Palace today 

The Entente Cordiale accord was signed in 1904 and cemented an improvement in relations after the Napoleonic Wars

A British member of the Number 7 Company Coldstream Guards walks past members of the French military and police towards the Elysee Palace

French President Emmanuel Macron and British ambassador to France Menna Rawlings walk in the courtyard of the Elysee Palace

Emmanuel Macron and British ambassador to France Menna Rawlings walk in the courtyard of the Elysee Palace

Emmanuel Macron and Menna Rawlings walk in the street outside the Elysee Palace

The ceremonies are seeing British guards take part in the changing of the guard outside the Elysee Palace of President Emmanuel Macron, while his French guards do 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, will relieve French counterparts from the first infantry regiment starting at 8:30am GMT.

The French army choir will then sing 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.

At the end of 2023, 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 will participate in the London ceremony alongside guards from F Company Scots Guards and other British forces, the French presidential official said.

It will be watched by the Duke and Duchess of Edinburgh - Prince Edward and his wife Sophie - accompanied by the UK chief of the general staff, General Patrick Sanders, and French chief of the army staff Pierre Schill.

The event on the forecourt of Buckingham Palace will mark 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.

Sophie, Duchess of Edinburgh, on behalf of King Charles, looks on at the Changing of the Guard at Buckingham Palace

France's Gendarmerie's Garde Republicaine arrive at Buckingham Palace to take part in the Changing of the Guard t

A member of the military band plays 'La Marseillaise' (the National Anthem of France) during the Changing of the Guard at Buckingham Palace

The Changing of the Guard takes place at Buckingham Palace

The signing of the Entente Cordiale on April 8, 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.