I can't imagine why Monsieur Collins is not often invited to high tea; perhaps it's muddy boots, or bad table manners; or, maybe it's prior knowledge of where lots of skeletons are buried. There are old fables about honour among thieves – then of course, conversely
A plague upon it when thieves cannot be true to one another ~ Shakespeare, Henry IV
We hang the petty thieves and appoint the great ones to public office. Aesop.