A pub is not a cocktail bar with worse drinks, so we don't score it as one. The Pour is judged against what the format is trying to do — a well-kept pint, a cask list worth reading, a cellar somebody looks after — which is why the Southampton Arms in Gospel Oak, seven rotating cask lines and a joint of pork behind the bar, beats every famous historic room in London on the two dimensions a pub competes on.
The oldest rooms are here and they are ranked honestly: Ye Olde Cheshire Cheese at nineteen, the Seven Stars at seven, Ye Olde Mitre at four. Each of their claims about age belongs to the pub making it, and we say so in the entries. The Blackfriar has the most beautiful interior in this corpus and is not on this list, because the beer is what a pub is for. Leading it is a 1949 Soho café-bar that isn't a pub at all and is open until four in the morning, which is the kind of thing a list ranked on scores rather than categories will occasionally tell you.
Also in London: The 20 Best Cocktail Bars in London and The 11 Hotel Bars in London.