Members of the King's Troop Royal Horse Artillery fire a 41-round gun salute to mark Queen Elizabeth II's 93rd birthday in Hyde Park of London, Britain, April 22, 2019. (Photo: Xinhua)

Members of the King's Troop Royal Horse Artillery take part in a gun salute to to mark Queen Elizabeth II's 93rd birthday in Hyde Park of London, Britain, April 22, 2019. (Photo: Xinhua)

British Princess Anne leaves after the King's Troop Royal Horse Artillery fired a 41-round gun salute to mark Queen Elizabeth II's 93rd birthday in Hyde Park of London, Britain, April 22, 2019. (Photo: Xinhua)

Members of the King's Troop Royal Horse Artillery fire a 41-round gun salute to mark Queen Elizabeth II's 93rd birthday in Hyde Park of London, Britain, April 22, 2019. (Photo: Xinhua)

A military band marches after the King's Troop Royal Horse Artillery fired a 41-round gun salute to mark Queen Elizabeth II's 93rd birthday in Hyde Park of London, Britain, April 22, 2019. (Photo: Xinhua)