[ddek]

err, kinda.

The North Circular is a decent enough road if you don't live by it.

I happen to live just by the South Circular, and it's not really a ring road. You wouldn't use it to circumnavigate London, it's just a joined up set of separate roads (of various sizes) that happen to form a vague semi-circle.

[alexfoo]

Also on the Eastern side there's only a ferry to connect the North and South Circulars. And that ferry has quite limited operating hours and capacity. It's also very slow.

To avoid the ferry you either need to come West a bit and use the Blackwall Tunnel or go way East and use the outer ring road (M25) crossings at Dartford.