Bear in mind the original reason for the 70 mph "national speed limit" wasn't road safety, it was fuel economy.
Rolfe.
I thought it was road safety....
http://www.information-britain.co.uk/famdates.php?id=280
Just before Christmas 1965 Transport Minister Tom Fraser (not Barbara Castle, as many seem to think) introduced a 70mph limit for drivers on motorways, following several pile-ups in the foggy autumn and winter of that year
The article goes on to repeat the claim that testing the AC Daytona was also a factor.