Prince William Leads Rehearsals for Dad King Charles' First Birthday Parade as Monarch

The Prince of Wales cast his eye over 1,500 soldiers and 300 horses that will take part in the Trooping the Colour parade on June 17

Prince William is leading the rehearsals for his father King Charles' big birthday parade.

The Prince of Wales, 40, cast his eye over the last big practice before Trooping the Colour, the annual public celebration of the British monarch's birthday, which will take place at Horse Guards Parade on June 17 this year. The festivities will mark the first birthday parade of King Charles' reign, although Queen Elizabeth held the annual event around the same time of year.

On Saturday morning, Prince William proudly ensured the Welsh Guards regiment — of which he's honorary Colonel — and the others from the household division were well-prepared for next Saturday’s parade. The Welsh Guards have the honor of Trooping the Colour at the parade this year – their flag will be presented in front of the King.

"The purpose of the Colonel's review is to decide that they are ready for the monarch," an army source told PEOPLE.

The Prince of Wales led the parade down the Mall in London on horseback. He wore the Guard of Honour Order, complete with a bearskin cap, tunic, garter sash and sword.

RELATED: Royal Family's Best Trooping the Colour Moments Over the Years — Including Prince Harry's Cheeky Face!

More than 1,500 soldiers and 300 horses from the Household Division of Welsh, Irish, Scottish, Grenadier and Coldstream Guards paraded for inspection by Prince William during the rehearsal. They carried out complex battlefield drill maneuvers to a program of music, which had what the prince’s office called "a distinctly Welsh theme." There were also some new tunes composed by members of the Band of the Welsh Guards specifically for the occasion.

The music and the parade will be viewed by the royal family — including Kate Middleton and Queen Camilla — and millions of television viewers next Saturday.

The parade will be a year of firsts — the initial one for the King and the first one for William as Prince of Wales. It was also the first time Prince William has taken on the rehearsal role since he was made ceremonial Colonel of the Welsh Guards shortly after the death of Queen Elizabeth in September. He did undertake the Colonel's review when he was Colonel of the Irish Guards last year — a role that now belongs to his wife, Princess Kate.

As the practice review took place on Saturday morning, Prince William’s office released some details of some of the duties the Welsh Guards have undertaken in the past year. They were part of the multinational force that designed and implemented the U.K. training package for Ukrainian soldiers “to gain the infantry skills they need to defend their homeland,” Kensington Palace said. "Alongside this, they have carried out jungle training exercises in Belize and Jamaica, as well as taking part in ceremonial duties for the Coronation of Their Majesties The King and Queen.”

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On the Welsh national holiday of St. David’s Day, March 1, Prince William was accompanied by Princess Kate, 41, as he took the salute at the annual Welsh Guards' parade and joined in the traditional festivities in the soldiers' mess.

The Trooping the Colour celebration next weekend comes during a busy public period for the royal family. The parade will be followed the next week by the Order of the Garter celebration at Windsor's St. George's Chapel and the Royal Ascot horse races.

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