Airport Bosses, and Police, that don't want the aggro, and don't want your uniforms
ISTR that BAA were more than happy for the boys in green to patrol outside LHR soon after 9/11, despite the fact that a Scimitar CVR(T) would be a poor counter-terrorist weapons platform.
Many years ago my Squadron (green, not cavalry, not signals, so work it out..) used to travel down the M4 to the land of the sheep quite frequently. The service station staff used to welcome us, and I'm certain that the lady dishing out the chips gave us all an extra portion. On one occaision there were some thugs scrapping in the car park and the duty manager asked us to go and sort it out as the Bill were miles away. Luckily it just took a few hard stares and they scuttled away.