The Star Tavern, Belgravia
I'll let you know about the beer once I've got out of chokey ;o)
6 Belgrave Mews West, Belgravia, London, SW1X 8HT
Leave Sloane Square tube, cross Sloane Square, and go straight up Sloane Street. Keep going for 5 minutes, then turn right down Pont Street. Follow this road as it changes into Chesham Place. Belgrave Mews West is on your left, just past the German Embassy.