XM520 was the last Britannia to be built at Filton, and the seventh aircraft of contract 15527. Wheeled out of the production hangar on 8 January 1960 and delivered to No. 511 Squadron Royal Air Force Transport Command on 19 March 1960 she was named 'Arcturas'. XM520 joined 99 and 511 Squadrons' Britannia pool on 22 March 1961 at RAF Lyneham. Withdrawn from use by the RAF, XM520 was stored at RAF St Athan, awaiting sale or lease from 14 May 1975. At the end of her RAF service she had 18 790.15 hours and 8446 landings logged. XM-520 was sold to Gemini Air Transport on 16 September 1975. The title Geminair was worn along with the new registration 9G-ACE, retaining most of the RAF colour scheme.

Redcoat Air Cargo Ltd operated 9G-ACE for one year from May 1976 on a dry lease and management contract until 6 May 1977. At the end of March 1981 9G-ACE had logged 25 646.37 hours and 9866 landings. She was registered 9Q-CUM, when purchased by Lukum Air Services in September 1981. Withdrawn from service and stored at Kinshasa, Zaire, she was sold to Katale Aero Transport for spares and broken up at Kinshasa in July 1986.