The system remained in place until technological improvements in the early 1960’s kick-started a major mechanisation programme.Machines replaced manual workers across the nation with postcodes being reduced to a machine readable form and printed on the envelope in phosphor dots.
More confusion derives from some London areas using postal addresses that refer to former county boundaries, for example postal addresses in Sutton traditionally read "Sutton, Surrey" and not "Sutton, London" even though Sutton no longer falls within the boundaries of Surrey County Council.
And some of the postal districts cross county and even regional boundaries - the KT postcode covers areas in both Greater London and the South East Region.
The numbering system also appears to be relatively random when looked at on a map.
For example, NW1 is close to central London, but NW2 is much further out.
Sir Rowland Hill’s system was based around compass points and an office established for each district which were organised and contained within a circle of 12 miles radius from central London.