Several British soldiers were overwhelmed by the heat and fainted this Saturday when they presented themselves in a formal manner in woolen tunics and bearskin hats to greet Prince William.

At least three guardsmen fainted during the military parade known as the Colonel’s Review, in which more than 1,400 soldiers from the Home Division and the Royal Horse Artillery Troop were reviewed by the heir to the throne, who is an honorary colonel of the Welsh Guards.

The temperature in London exceeded 31 ºC (88 F). William then tweeted: “Thank you so much to all the soldiers who participated in Colonel’s Review this morning despite the heat. Difficult conditions, but you all did a very good job.”

The event was a rehearsal for Trooping the Colour, an annual military parade held every June to mark the monarch’s official birthday. King Carlos III will oversee the ceremony on June 17.