Two things you should know about me; The first is that I am deeply suspicious of people in general. It is my nature to expect the worst of them. And the second is that I am unexpectedly good with computers.
There's lots of people will help you with alcohol business, but there's no one out there arranging little meetings where you can stand up and say, 'My name is Sam Vimes and I'm a really suspicious bastard.
I also think he is given to disguises...Sometimes he wears spectacles and sometimes he does not. And twice he has worn an extremely peculiar hat. Inside.
"Not being invited in is one of the boxes on the "suspicious behavior" bingo form that every copper carries around in their head along with "stupidly overpowerful dog" and being too quick to supply an alibi. Fill all the boxes and you too could win an all-expenses-paid visit to your local police station."