"History of the Imperial War Museum" The Vickers QF 13pdr Horse Artillery Gun of E Battery, Royal Horse Artillery, leaves the Imperial War Museum's building in South Kensington, to take part in the unveiling of C S Jagger's Memorial to the Royal Artillery at Hyde Park Corner, London on 18 October 1925. During the First World War, the gun fired the first British round on the Western Front on 22 August 1914 and was also one of the last to fire before the Armistice came into force in 1918.