Soldato
This does surprise me. It doesn't send a very good image. If you see a copper in uniform you should expect to be able to approach them as if they are on duty, going up to one that's getting 4 tinnies of Stella hmmm. I'm surprised they're allowed themselves, regardless of a shopsellers rules.
Are you saying that nurses, firemen, military are all still people you can't serve alcohol to, but you are allowed to the police?
The pub may be allowed to serve it but I will bet there are regulations in the Police that will not allow cops in uniform to buy alcohol.

