My XFR managed 165 and I slowed down while it was still happy to go faster, despite being supposedly limited to 155. The GTS made 150mph at Brunti but others managed more - clearly my exit speed from the chicane was too low. TomTom and Maser speed readout are pretty much bang on - a difference of around 2mph at around 70 (never faster on a public road, no way at all).
Pete - your dad sounds proper old school.
An old friend's father was pulled over many years ago on a Saturday night, all the family in the car. "Have you been drinking, sir?". "Of course I've been bloody drinking. I've been out to dinner." Scott free. Something big in the Masons, apparently.