M25 motorway re-examined as a motorway route in Sir Charles Bressey's and Sir Edwin Lutyens' "The Highway Development Survey, 1937". Sir Patrick Abercrombie's "County of London Plan, 1943" and "Greater London Plan, 1944" proposed a series of five roads encircling the capital. The northern sections of the M25 follow a similar route to the World War II Outer London Defence Ring, a concentric series of tanks and pillboxes designed to slow down a potential German invasion of the capital. Little was done to progress these plans until the 1960s when the Greater London Council developed its London Ringways plan consisting of four
M25 motorway "rings" around the capital. Sections of the two outer rings – Ringway 3 (the 'M16 motorway') and Ringway 4 – were constructed in the early 1970s and were integrated into the single M25 orbital motorway. But the Ringways plan was hugely controversial owing to the destruction required for the inner two ring roads, (Ringway 1 and Ringway 2). Parts of Ringway 1 were constructed (including West Cross Route), against stiff opposition, before the overall plan was abandoned in 1973 following pressure from residents in the threatened areas. Construction of parts of the two outer ring roads, Ringways 3 and 4,