For the control of Civil Defence services England, Scotland and Wales were split into various areas. Region 5 covered the 28 Metropolitan Boroughs (forming the London County Council) plus the City of London and the County Boroughs of Croydon, East and West Ham and a number of small urban rural districts in Essex, Kent, Middlesex and Kent.
Various local authorities were then combined into Groups - numbered 1 to 9 across the region. Groups 1 and 2 were later combined into just Group 1 in 1943. Within a single group each authority would have a control room and one of the authorities would also have a group control.