A2
A2 and A2(M)
London's ancient main road to Canterbury and Dover has been bypassed over and over again, and in the sixties was supposed to be replaced in part with an urban motorway. Parts were finished in the end, even if they weren't quite to the original designs.
Routes
East Cross Route
The strangest part of London's planned inner Motorway Box - not just because it's nothing like the other three sides, but also because it actually got built.