Spur Battery was completed in 1902, 1,130 feet above sea level, near the top of the Rock. The barrel of the gun now displayed at Duxford Airfield replaced the original barrel at Spur Battery in 1929. It had first been issued in 1903 as a Mark 10 and relinered to Mark 10 standard in 1919, but nothing is known of its service during that period. The gun carriage was converted in 1935 from a Mark 5 to a Mark 7, which provided improved loading, elevation and traverse. Since 1935 the gun has fired 596 rounds. It was last in action in 1973, when 29 rounds were fired at a towed target which received several direct hits. The dismantling of the gun and its movement to the Gibraltar dockyard (Project Vitello I) were exceptionally complex and demanding tasks. The operation was carried out in the Spring of 1981 by 61 Field Support Squadron of 36 Engineer Regiment, Royal Engineers. Access to Spur Battery and working space around the gun were extremely restricted, and the major components had to be removed by traditional methods, using jacks, skates and winches. Project Vitello II began in August 1981 when the gun arrived at Portsmouth on board the Royal Fleet Auxiliary Vessel Bacchus. It was moved to Duxford in eleven loads by 56 Motor Transport (Training) Squadron Royal Engineers. The gun was reassembled by 34 Field Squadron of 39 Engineer Regiment, Royal Engineers. The Trustees of the Imperial War Museum owe a great debt of gratitude to the Royal Engineers for their part in Project Vitello.