Not a prototype paint scheme
This is a Regt HQ tank from BATUS or rather a privately owned Chieftain (01 EB 90) painted up to look like a BATUS Chieftain with the "Chinese Eyes" of 4 RTR - with the Scottish Saltire which I presume was because they recruited mainly from Scotland after the end of the 1960's and some amalgamations. .
Its been doing the UK show scene for years now.