We are proud to say that our maps are based upon Ordnance Survey maps and always have been. However, while OS is our main source of revision we also gather additional information from other official bodies and our own site visits to keep our maps as up to-date as possible. This 1970’s compilation overlay shows the alignment of the proposed M25 to the west of London and junction 12, the M3 Thorpe Interchange, plotted by an A-Z draughtsman from large scale side road order plans. The blue pencil indicates detail that should be deleted in connection with this road scheme. Changes to the lakes in the top right quarter of the image are part of the planned Thorpe Park which opened in 1979.