By the end of the 19th century, Victorian London had expanded as far north as Hampstead, beyond which lay the cottages, fields and wilds of Middlesex. It was here that from 1907 the Hampstead Garden Suburb was built around what was to become the Heath Extension. Join Calum Orr, Architectural Adviser to The Hampstead Garden Suburb Trust, on a walk from the hamlet of North End to the Suburb, as we try to gather a picture of the still-visible landscape at this decisive moment.