Why The SSK probably didn't win
Whilst the RB211 was built in Derby the RB stood for Rolls Barnodswick, where the engine was designed. As for it being a "Derby Winner", the problems with the engine hardly made it a winner at the time BA received its L1011s as the problems with the engine crippled Rolls Royce, damaged the government, cost the taxpayer and seriously delayed the delivery of the aircraft.
BA would hardly have wanted a reminder to its passengers and staff painted on the aircraft.