The Avro Vulcan (later Hawker Siddeley Vulcan[ from July 1963)[3] is a jet-powered tailless delta wing high-altitude strategic bomber, which was operated by the Royal Air Force (RAF) from 1956 until 1984. Aircraft manufacturer A.V. Roe and Company (Avro) designed the Vulcan in response to Specification B.35/46. Of the three V bombers produced, the Vulcan was considered the most technically advanced and hence the riskiest option. Several scale aircraft, designated Avro 707, were produced to test and refine the delta wing design principles. Since retirement by the RAF one example, B.2 XH558, named "The Spirit of Great Britain" was restored for use in display flights and air shows, whilst two other B.2s, XL426 and XM655, are kept in taxiable condition for ground runs and demonstrations at London Southend Airport and Wellesbourne Mountford Airfield respectively. B.2 XH558 flew for the last time in October 2015, before also being kept in taxiable condition at Robin Hood Airport, Doncaster.