Hotel Bar
No cask ale, but the bar and grill is open to non-residents, the entrance being to the right on entering St Ermin's Hotel. Four keg beers are on offer plus an array of cocktails and spirits etc.
This is part of a very up-market hotel, so food should be available somewhere most of the time.
A service charge of 12 1/2% is added even if you are just sitting at the bar.
Caxton Bar & Grill, London