It is obvious from the outside that the Bag of Nails is no ordinary pub. Two sleeping cats are visible, curled up on the windowsill, and a big sign warns visitors that no dogs are allowed, due to “pub kittens in training.” Inside, standing at the bar and ordering a drink, I am watched by one cat slinking along the bar, another half-dozing in an empty tonic box, and two more on a bench and a chair behind me. The Bag of Nails pub, by the Floating Harbour in Bristol,…