The early 20th century, especially during the interwar years of the 1920s and 1930s, saw the geographical extent of London’s urban area grew faster than at any point before or since. Most of the development was of suburban expansion into the neighbouring counties of Essex, Hertfordshire, Kent, Middlesex and Surrey. A preference for lower density suburban housing, typically semi-detached, by Londoners seeking a more “rural” lifestyle, superseded Londoners’ old predilection for terraced houses. The rapid expansion of London during this period swallowed up large swathes of countryside. Fears over the loss of countryside led eventually to the introduction of the Metropolitan Green Belt, restricting urban growth.
This meant that London outgrew the boundaries of the County of London, which led to calls by the London County Council for the creation of a single Greater London authority covering the entire urban area, although this was rejected by the Royal Commission on London Government in 1921.