Marylebone is the bit of central London that got rich without getting loud. A two-and-a-half kilometre loop takes you past Daunt Books, up the high street, through a pocket garden, down Chiltern Street, and back out by the parish church.
Start at Daunt; everyone does, for good reason. It's still the most beautiful bookshop in London and the staff still actually read. From there the high street is a five-minute slow browse — La Fromagerie for cheese, Aesop for soap, a series of boutiques whose business models I don't fully understand.
Cut west through Paddington Street Gardens, which is a former burial ground that has quietly become the nicest pocket park in zone one. Turn down Chiltern Street — nominally a shopping street, actually a series of small architectural set-pieces — and loop back past the parish church to where you started.
Forty-five minutes if you don't stop. Ninety if you do. Two hours if you go into Daunt first.
