Our new home is 20 miles from Northampton - about 50 minutes drive for most of us, about 7 minutes if he could do that speed all the way. The roundabouts and artics (articulated lorries, or what you call semi-trailers) would slow him up a bit

Seriously, the word cretin is too good for him and his death-wish daughter, who was encouraging him. However, it was considerate of him to provide photo evidence for the fuzz ;-)
For the record, national speed limit in the UK is 70mph on motorways and dual carriageways and 60mph on single carriageways. And the Silverstone F1 race track is in Northamptonshire where, as you observe, only suitably qualified drivers are allowed.
And, Frances, I'd never heard of that one...