That is what I read, but the officer apparently never mentioned that to her at all, which struck me as a strange omission on his part.
Perhaps I shall take it as an excuse to upgrade my radar detector and give her my existing one...!
A radar detector isn't necessarily going to save here. Going 20km/h + over the speed limit is dangerous and very obvious. Even in a Police car sees you at this speed and doesn't have their radar on you'd still get pulled over as it's going to be pretty obvious especially if it was a 50 km/h area.
Pulled over and warned though... There's nothing else they could do in terms of speeding without proof. Sure they could give the car a good going over - but assuming you stayed in lane and didn't tailgate someone they couldn't even hit you with dangerous driving for 70 in a 50.
Cheers - N