In the mid-1970s, the A405 was extended from Leavesden Green. This extension ran concurrently with the A41 to Hunton Bridge, then continued westwards over the River Gade and past the hamlet of Chandler's Cross. It then veered south to pass between Rickmansworth and Chorleywood, crossing the River Chess, the A404 (with which it had a grade-separated junction) and the London to Aylesbury and London Underground Metropolitan lines. It ended just north of Maple Cross, at the A412, on which the "North Orbital Road" continued south to Denham in Buckinghamshire. This took the length of the A405 to 16.3 miles (26.2 km).