... an active motorway carrying up to 120000 vehicles per day, its proximity to built-up areas in the metropolitan green belt and its proximity to an existing junction between the M1 and the A405 The final choice was a four-levelinterchange and the selection of suitable forms for the central structures...

... was openedto traffic asthe A1178, laterdesignated M25 which had its origin in the south of the ring where the M25 was in fact a bypass of the A25 2. Traffic andenvironmentalconsideration led tothelocation of the M25 largely within the Metropolitan Green Belt and the finger of development up the Lea Valley...