Breaking News:Fans Blast Prince Edward and Sophie Stand in for King Charles During a Royal First at Buckingham Palace

The Duke and Duchess of Edinburgh watched French soldiers take part in the Changing of the Guard for the first time.

Prince Edward and Sophie, the Duchess of Edinburgh took part in a historic Buckingham Palace ceremony on Monday as King Charles continues his treatment for cancer.

Tourists watching the traditional Changing of the Guard through the railings witnessed the unique treat of watching French troops join their British counterparts in an unprecedented move for the daily ceremony.

King Charles asked his brother Edward, 60, and sister-in-law Sophie, 59, to stand in for him at the special parade in honor of the 120th anniversary of a key diplomatic agreement between the U.K. and France known as the “entente cordiale.”

Since his cancer diagnosis, which was announced on Feb. 5, King Charles continued to work behind the scenes but has not been able to carry out most of his public duties. On previous occasions, his wife Queen Camilla, 76, has stepped in for him, but he asked his youngest sibling and Sophie to do so on Monday.

Shortly after arriving at the palace forecourt, Prince Edward, Sophie and the French ambassador to the U.K., Her Excellency Hélène Duchêne, inspected the troops. In front of them, 32 members of the Gendarmerie’s Garde Républicaine joined 40 Guardsmen from the Scots Guards. It was the first time that soldiers from a non-Commonwealth country had joined the ceremony.

In a parallel move, 16 soldiers from Number 7 Company Coldstream Guards, accompanied by two military musicians, joined troops from 1st Régiment de la Garde Républicaine to provide the Presidential Guard outside the Elysée Palace, in Paris. Like London, it was the first time a foreign state helped guard the French Presidential Residence. The troops were inspected there by French President Emmanuel Macron.