Sam Smith's like rules for all, behind and in front of their 300-odd bars. It's never entirely clear which of the Smith dynasty writes the edicts - father, brother, son - but they're all very particular about cleanliness, polishing and conformity.
Now there's a chain wide-edict banning swearing, and helpful posters with "No Swearing" in block letters (“We wish to inform all of our customers that we have introduced a zero tolerance policy against swearing in all of our pubs. Please kindly respect this policy”) have been issued to pub managers. Brief and unsystematic research has yet to spot one of the posters actually pinned up.
Still, if BBC hacks get a bit too tense in the election campaign, there could be the odd flare-up with bar staff around Broadcasting House. And if you seek a haven of debate without resort to potty-mouth stuff, here's a handy map.