Forty-five Jermyn St lives in the left-hand buttock of Fortnum & Mason (F&M), a shop whose acronym is slightly too close to FGM (female genital mutilation) for this column to be able to relax there for long periods, even though its Diamond Jubilee Tea Salon is excellent. Its name is part of a vogue for naming restaurants after postal addresses, and even street numbers (Richard Caring’s 34 in Mayfair).