What is the main highway through London?

The A406 North Circular Road, also known as the North Circular, is the most significant main road in London. It is a ring road that encircles London from Chiswick in the west to Barking in the east, where it connects to the A13 in both directions. The A406 is one of the busiest roads in the UK and is the primary route used by lorries and other commercial vehicles to access London.