I only ever went through London from our area when I was a fitter to tow trucks back to our quarry that expired in the Capital! That was in the late 70’s which involved M1/M10 then down through Potters Bar, Cockfosters and over the North Circular onto the A10 down through Stamford Hill and Clapton Common, around Hackney Hospital and then through the spout! It was fun coming back with a Gardner 180 engined Foden S80 tipper with ten tons on its back towing a fully laden Foden eight legger and pedestrians walking between them and tripping over the tow bar when you stopped at traffic lights etc. 
The 1 in 5 hill out of Ashbourne made the Gardner work hard pulling 50+ tonnes as well. 
When I lived in Reading I travelled to Waterden Road, Hackney most fridays in the early 70’s but I can’t remember the route now. 
Pete.