So in London, we used the iPhone, and it was great, but driving was terrifying. I honestly don't remember which of us was driving and which was navigating, but the whole thing was harrowing.
I will say that I am my father's son, as my memory is that we laughed the whole time, and if my father had been with my mom, or I had been with my wife, it would have been way less funny…
Anyway, eventually we left London and were where we needed to turn to the Garmin data.