Guns sound to mark Queen's 86th Birthday The King's Troop Royal Horse Artillery fired the salute at noon in Hyde Park while several other military bases across the country also carried out the tradition in honour of the Queen's birthday. The custom dates back to the early days of sail when ships visiting foreign ports would discharge their guns before entering, proving they were empty and that the visit was peaceful. A basic salute uses 21 rounds, but in Hyde Park an extra 20 rounds are added because it is a Royal Park. The Queen's birthday is one of six royal events that are marked annually with traditional gun salutes. The Royal Navy fired a 21 gun salute at Fort Blockhouse at Gosport, Hampshire - at the entrance to Portsmouth Harbour. The portable 19th century gun at Fort Blockhouse has been firing salutes since it was acquired by the Navy in 1957. To mark the Queen's birthday, Royal Navy ships at Portsmouth Naval Base were "dressed overall" - displaying a variety of flags across the length of the ship. Crowds also gathered at Edinburgh Castle to watch gunners of 207 Battery, 105 Regiment Royal Artillery (Volunteers) to fire a salute to the Queen. Stirling Castle also rang to a 21-gun salute fired by the 212 (Highland) Battery.