" 'Ascot', obviously inspired by the 10 Sqn callsign".
The whole of Transport Command became Air Support Command on 01 August 1967. 10 Sqn had absolutely nothing whatsoever to do with the ASCOT callsign.
I quote from my history of 53 Squadron:
"Transport Command was given the new title of Air Support Command on 01 August. Wg Cdr Basil Taylor, who had been OC No.53 from 1958 to 1960 (Beverleys) was working in the Ministry of Defence at the time and saw this as a golden opportunity to find a new radio callsign to replace the old "RAFAIR" version. He was a keen student of the racehorse and, in cahoots with Wg Cdr Basil D'Olivera, OC No.216 (VIP Comets), came up with "ASCOT". This was officially expained away to his seniors (VCAS) when submitted for approval, as standing for "Air Support Command Operational Task". The callsign is still in use to this day!"