Hedge
The first bit of motorway in the country was the Preston bypass in the early 60's, it was a short stretch that eventually became the M6.
Your urban legend is true but Im very proud to say that it was my Dad who used to own the 5 Barred Gate garage, near Salmesbury who used to use this super smooth piece of Tarmac to road test his race prepared XK120's and E Types. He'd converted from stock by using Alloy Panels and wide angle heads directly from the Fire escape door of Browns Lane!
he eventually ended up with 4WPD which was the very best works development lightweight e Type, one of the first race cars with Fuel Injection. Other drivers of that car were Graham Hil, Jackie Stewart, Roy Salvadori and many others....
My dad had a visit from the then chief constable who was based in Hutton Nr Preston and told him to basically pack it in....
Just to set the scene, you're a copper sat on the side of the road in a 30hp morris and this thing goes past.....they never ended up bothering chasing him!
http://www.fiskens.com/pages/common/flash.aspx?pg=239