The position of Gold Stick is held by the Colonels of The Life Guards and The Blues and Royals, both regiments of the British Army, and whoever is on duty at the time is referred to as Gold Stick-In-Waiting. Princess Anne was appointed Colonel of The Blues and Royals in September 1998, per The Gazette. However, King Charles III’s coronation and State Opening of Parliament ceremonies were the first times the Princess Royal has been the official on duty.
A source told Daily Mail that Charles’ decision to include his younger sister in the ceremonies was his way of “rewarding the Princess Royal for her loyalty and her unwavering devotion to duty above all else. The King values his sister as a trusted lieutenant, and this is the perfect example of such a relationship.” Sources told the newspaper Princess Anne was “incredibly honored” by her brother’s decision.
In addition to serving as the Gold Stick-in-Waiting, Princess Anne is a Counselor of State with her younger brother, Prince Edward. If Charles cannot perform his monarch duties due to illness or traveling abroad, Princess Anne will be able to take over his constitutional responsibilities through the Counsellors of State Act 2022 (via UK Legislation).