Built to Contract 11804 to provide the Ministry of Supply with 3 Britannia Aircraft dated February 1955. G-APPG's first flight was on 2 March 1959 in civil markings. Operated by A&AEE Boscombe Down for evaluation purposes from 8 April 1959. Early April 1959 she was painted in Royal Air Force Transport Command markings, registered as XN404. Allocated to No. 99 Squadron on 6 April 1959, she was named 'Canopus'. In RAF service the series 252 was known as the C Mk2. She was pooled at RAF Lyneham on 27 February 1961.

Withdrawn from RAF use on 17 July 1975, XN404 was ferried to RAF St Athan for storage and re-sale. Purchased by Shackleton Aviation on 17 December 1975 she was flown to Hurn Airport the same day. Air Faisal were to purchase XN404 after its delivery to Luton Airport, but this never took place. XN404 totalled 13 865 flying hours and had carried out 9862 landings. During November 1976, XN404 was broken up and scrapped on behalf of Air Faisal.