Prince Philip at Trooping the Colour only week after leaving hospital On Friday night Prince Philip was the host at a dinner at Buckingham Palace, acting in his role of Colonel of the Grenadier Guards He was released from Edward VII hospital on 9 June, a day before his 91st birthday. The Duke of Edinburgh had appeared to be in good health when he accompanied the Queen on the royal barge, the Spirit of Chartwell, for the Diamond Jubilee river pageant, on 3 June. But his admission to hospital the next day meant that he could not join the Queen at the final events to mark her 60 years on the throne, including a concert outside Buckingham Palace and a royal procession and appearance on the palace balcony. He also missed three days of engagements earlier this week as he continued to convalesce, which included a Jubilee garden party at Sandringham, Norfolk, and the Queen's visit to Nottingham. The Colour being paraded on Horse Guards this year was the flag of the 1st Battalion Coldstream Guards. There were 241 horses on parade, with 290 musicians marching and playing as one. The Kings Troop Royal Horse Artillery were set to fire a gun salute in Green Park, while the Honourable Artillery Company were firing a 62-round Gun Salute from The Tower of London to mark the Queen's official birthday. After the Queen took the salute on Horse Guards, the royals were set to head back to Buckingham Palace to gather on the balcony to watch the traditional RAF flypast. Ahead of the parade, the Queen received birthday wishes from US Secretary of State Hillary Clinton, who hailed a "special history of friendship" with the UK. She said: "The United States has long viewed the Queen and her service to her nation with the deepest respect. In this Diamond Jubilee Year, her tireless dedication is a beacon of hope to peoples and countries around the world. Mrs Clinton added: "I send Queen Elizabeth II and the British people my most heartfelt congratulations on this special day. Best wishes for a year of peace, prosperity and happiness. Trooping the Colour originated from traditional preparations for battle. Colours, or flags, were carried or "trooped" down the rank so that it could be seen and recognised by the soldiers. In the 18th century, guards from the royal palaces assembled daily on Horse Guards to "troop the colours," and in 1748 it was announced that the parade would also mark the Queen's official birthday. The Queen's actual birthday was on April 21, when she turned 86.