Then came the 1974 fuel crisis which, apart from producing the national speed limit of 70 mph (it was nothing to do with road safety)
The 70mph national speed limit was first introduced as a temporary measure in 1965, and made permanent in 1967. The 1974 fuel crisis lead to a 60mph limit on dual carriageways, and 50mph on all other roads except motorways, where the 70mph limit still applied.
Anyway, please forgive the digression, and many thanks for all the Trident stuff.