Semi-detached houses for the middle class began to be planned systematically in late 18th-century Georgian architecture, as a suburban compromise between the terraced houses close to the city centre, and the detached "villas" further out, where land was cheaper. There are occasional examples of such houses in town centres going back to medieval times. Most early examples are in areas such as Blackheath, Chalk Farm and St John's Wood, now the outer fringes of Central London. Sir John Summerson considered the origin of the semi-detached house to be the Eyre Estate of St John's Wood. He commented that in a plan for the estate dated 1794 "the whole development consists of "pairs of semi-detached houses". So far as I know, this is the first recorded scheme of the kind." The estate was not built at that time due to the French Revolutionary Wars, but when it was finally built it retained the semi-detached form, "a revolution of striking significance and far-reaching effect".