The Colonel's Review is the second rehearsal for Trooping the Colour, the ceremonial event marking the official birthday of Queen Elizabeth II. The last time event took place was in 2009.
"As Colonel of the Irish Guards, The Duke of Cambridge is attending The Colonel's Review for the first time today. The Colonel's Review is a military rehearsal for The Queen's Birthday Parade, also known as Trooping the Colour, on 17 June," read the official statement from Kensington Palace.
According to BBC.com, the 34-year-old royal inspected the troops as more than 6,000 people watched from The Mall. There were more than 200 military horses and 400 musicians that participated in the rehearsal.