is famously fuss-free in her approach to royal duties, but couldn’t resist putting her in the spotlight on her 73rd birthday. His Majesty used the official Royal Family Instagram account to send public well-wishes to her younger sister, alongside two photographs capturing their lifelong bond. The first, a behind-the-scenes photo from the coronation, shows King Charles and Princess Anne smiling at each other in a quiet moment between . The occasion was an important moment for Princess Anne as she embraced her responsibility as one of the monarch’s most trusted advisors by serving as Gold-Stick-In-Waiting and travelling directly behind the King and Queen’s carriage. The second photo shows a young and Princess Anne at home in Clarence House in July 1951, just before Anne’s first birthday. The black-and-white image shows the royal siblings in their pushchairs, with Prince Charles leaning across to coo over his baby sister, who looks precious in a knitted bonnet. The accompanying caption reads: ‘Wishing Her Royal Highness a very Happy Birthday today!’ Dubbed King Charles’s ‘secret weapon’, Princess Anne has proved herself time and time again as a trusted member of the Royal Family with an unwavering sense of duty. She was a doting daughter to her parents, and Queen Elizabeth II, with whom she shared a wonderfully close relationship right up until their deaths. Prince Philip was always so proud of his only daughter, who shared his competitive streak, direct approach and low-key approach to official engagements. Meanwhile Princess Anne, a former Olympic equestrian, inherited her passion for horses from her mother. During her mother’s record-breaking reign, Anne was honoured with senior military positions and key responsibilities at Trooping the Colour and Jubilee celebrations. Following the death of Queen Elizabeth II in September 2022, it was Princess Anne who . King Charles trusts his sister implicitly. ‘She is the person the King has known longest,’ royal commentator Wesley Kerr OBE previously told . ‘She can be relied on for complete discretion and unconditional love. Anne is wise, intelligent, incredibly plugged into the modern United Kingdom. She understands completely who and what has shaped him and is eager for him to succeed: for the sake of their beloved mum and dad and for country and Commonwealth.' Zenouska Mowatt, Princess Alexandra's granddaughter, added: ‘Ask anyone about the Princess Royal and there would be a resounding show of support for the dedication and hard work she puts into her role. She does it with such ease; she is an inspiration and a superhero figure, really.’ , Anne was given a starring role. As the newly crowned King and Queen left Westminster Abbey in the Gold State Carriage, they were followed by the Princess Royal, 72, on horseback, performing the prestigious ceremonial role of Gold-Stick-in-Waiting. She led 6,000 members of the armed forces from the Abbey, down to Buckingham Palace. At Trooping the Colour, the first of the new reign, Princess Anne rode on horseback alongside , the Duke of Edinburgh, and . Once again, she was front and centre on one of the biggest days of her brother’s life. Yet Princess Anne has never courted the spotlight. In recent months she has made , preferring to let her work speak for itself. This might give the impression that she is less prolific than other more public members of the Firm but in fact the opposite is true: even in her 70s, Princess Anne is often named one of the hardest working . Her standing within the family has only risen in the wake of the double duke scandal of ’s departure from the Royal Family and ’s cloud of controversy. It is not known how Princess Anne will mark her birthday but she will no doubt be showered with love by her family – husband Vice Admiral Sir Tim Laurence, children and Peter Phillips, and grandchildren Savannah and Isla Phillips, and Mia, Lena and Lucas Tindall. The next few weeks will be particularly poignant for Princess Anne and the rest of the royals prepare to mark the first anniversary of the death of Queen Elizabeth II, but as King Charles’s Instagram post proves, she will have her brother by her side through it all.