Do any english police officers, or any other organization bear this badge?

today me and a couple of mates were on the bus(uk), double decker. We were at the 2nd floor and my mate was throwing food out of the windows(we usually do that). some old lady comes to us and shouts at us, and she then flashes a badge wich said 'GRAIL' on it. Bear in mind in the uk, our police is the metropolitan police, i know that throwing food out of the bus is wrong, but so is impersonating a police officer. any police officers in london that have a badge that says 'grail' on it?