Skyways transferred their Constellations to Euravia in September 1962, retaining one on lease from Euravia until April 1964. So in 1964 a Constellation sat out on the apron edge would almost certainly be one of Euravia's. Euravia became Britannia Airways August 1964 on acquiring Britannia 102s from BOAC. Their final Constellation was retired August 1965.
Viscount .... Well that is just taking the biscuit!