In message . com,
Boltar writes

as the M23 originally supposed to have continued further north than it
does now?

Yes, it was to have continued as far as Balham, from where spurs would
have connected it to the inner London Ringway ("London Motorway Box").
The only bits of the latter to be built were the sections either side of
the Blackwall Tunnel, plus the tiny bit of (former) motorway from
Westway down to the Shepherd's Bush roundabout:

http://upload.wikimedia.org/wikipedi...1960s_Plan.png

Everything else was abandoned due to the cost and unacceptability of
demolishing tens of thousands of properties.

--
Paul Terry