Family matter: Prince William (40) has the last rehearsals for his father's big birthday parade, King Charles III. (74), directed.

As reported by "People", the prince was carefully watching over the last rehearsals before the public "Trooping the Color" parade on June 17. It will be the first birthday parade for King Charles during his reign.

Prince William "proudly" went about his task on Saturday morning, writes "People". Accordingly, the prince made sure that the Welsh Guards, the youngest guard regiment in the British Army, are as well prepared as possible for the parade next Saturday.

The Prince of Wales, who is Honorary Colonel in the Welsh Guards, led the parade on horseback down the Mall in London. He came in full gear: bearskin hat, tunic, garter belt and sword. The Welsh Guards have the honor of flying their flag to the King at the parade this year.

A total of more than 1,500 soldiers and 300 horses marched forward for inspection by Prince William during the rehearsal. After the rehearsals, William tweeted: "A big thank you to all the soldiers who attended the Colonel's Review in the heat this morning. Difficult conditions but you all did a really good job. Thank you. W."

Due to the oppressive temperatures in London, several soldiers had passed out during the exercise and had to be taken from the field, some on stretchers.