Ordered by the Royal Air Force in November 1955 and built to contract 12829, this aircraft was delivered to 99 squadron Royal Air Force Transport Command on 5 August 1959 and once taken on charge on 7 August was serialled XL638, named 'Sirius', designated a C mk l. Following the pooling of 99 and 511 Squadrons Britannia fleet at RAF Lyneham, Wiltshire, XL638 was operated within the pool from 30 June 1960. XL638 disgraced herself on 12 October 1967 when she overran the runway whilst landing at RAF Khormaksar, Aden. Unfortunately she was damaged beyond repair and written off. Thankfully no lives were lost and the Bristol Britannia in RAF service kept her unblemished record... apart from this little episode! Because of her close proximity to the runway following her accident, it was decided to remove the tail section by an extreme measure 'it was blown off! XL638 had flown 9371.30 hours and made 3700 landings.