The Blackbuck arrived with Pair of Waterbuck,and Bactrian Camels in around 1983 from Marwell and ZSL
Well that's interesting as Marwell's very first pair of Blackbuck came from Colchester! These were handraised animals originally from ZSL and the buck was pugnacious as a result. This pair + one male offspring were later sent to Paignton Zoo.
Marwell also received 1.5 Blackbuck from Copenhagen- a male offspring of the original(ZSL/Colchester) pair was also kept so the ones that went back to Colchester may have been partly related to their original ones.
Do you know where Marwell's Blackbuck went when they stopped keeping them. Was it Cotswold by any chance?