The 1st Battalion Welsh Guards celebrated St David's Day in Windsor with the Prince and Princess of Wales.
The Princess and Prince William, the new Royal Colonel of the Welsh Guards, attended the celebration with the battalion which is 91% Welsh.
The Welsh Guards paraded at Combermere Barracks in Windsor, alongside the Band of the Welsh Guards on Wednesday.
They were presented with leeks, an emblem both traditional and central to the battalion, by Prince William while the Princess of Wales handed out leeks to family members at the parade.
After three cheers for the Prince of Wales, the Welsh Guards marched off the parade to continue the celebrations with their families.
After an official photo to mark the milestone, the Prince and Princess of Wales were escorted to a reception to meet members of the battalion and their loved ones.
Commanding Officer Lieutenant Colonel John Livesey said the day is special for the battalion as it marks the day they "mounted our first King's Guard and began our service to the Monarch" in 1915.
"It is therefore particularly special and fitting that on St David's Day, we get to welcome HRH the Prince of Wales into the family as our new Royal Colonel," he said.
"Cymru Am Byth (Wales forever)."
Traditionally marking the start of Spring, St David's Day is also a marker of the Guards' change of role – from operational to ceremonial.
The battalion's dual-role soldiers will now begin preparing for the Coronation of King Charles, as well as His Majesty's birthday parade, at which they will Troop their Colour.