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
West London Orbital Line, Bakerloo Line, High Speed 2, Crossrail and the Piccadilly Line. It is anticipated the line will be operational by the mid-2020s, reflecting the fact that it makes use of existing under-used rail infrastructure rather than requiring significant lengths of new track or tunnels to be built. An unrelated scheme of the same name was previously proposed in June 2008 by the West London Business group. That proposal involved the construction of a new underground line across West and South West London and did not progress beyond concept stage. The West London Orbital line consists of a number of distinct