Prince William led the rehearsals for his father King Charles' birthday parade, but it didn't go that smoothly.
During the Colonel's Review at Horse Guards Parade on Saturday,
a trombonist, who is a member of the Band of the Welsh Guards, fainted while wearing traditional guard attire and was later carried out by a stretcher.
According to the Associated Press, at least two other Guardsmen fainted as well.
Following the incident, Prince William praised the Guardsmen who took part in the rehearsal under "difficult conditions".
"A big thank you to every soldier who took part in the Colonel's Review this morning in the heat. But you all did a really good job",
the official Twitter account for The Prince and Princess of Wales tweeted.
Temperatures hit the mid 80s in London on Saturday.
This year's Trooping of the Colour is set to take place next Saturday, marking King Charles' first annual birthday parade as official King of England.
The 74-year-old was officially crowned monarch last month.