I'm almost sure the horse's name was Burmese, he was retired aged 35 in 1986. The Queen decided that she didn't wish to train another horse to take his place, and thereafter she would ride to the Trooping of the Colour in an open Landau.
It was called, 'The Big mare supporting the even bigger mare one Top! Now this was translated from the old lost language from a far off distant land and was better known as= BMS EBM OT = and there ye go!