An unmarked grey door with a digi-code entry pad in a King’s Cross backstreet marks the spot. To proceed further, you’ll first have to negotiate with the owners of Drink, Shop & Do (a social club/bar on Caledonian Road), but if you succeed you’ll cop free membership for Keystone Crescent. With its sophisticated muted tones, tactile texturing and smart 1950s hire-purchase ‘settees’, this debonair basement could be a set from Mad Men– save for some more modern hooch behind its small timber-topped brick bar. Aimed at ‘sociable people who like straightforward drinks until unsociable hours’, it offers a dozen wines by the bottle with painless mark-ups either side of £25, plus fairly basic cocktails, a selection of zesty homemade shrubs to pep up a Broker’s gin (or your spirit of choice) and some of London’s coolest customers