MONDAY - On an early flight to Tokyo for the biennial motor show, but first to take up an enticing offer from Nissan to try one of its autonomous driving prototypes. This boiled down to accompanying a test driver in a self-driving Leaf on a lightly trafficked 20-minute route across Tokyo Bay via a newly built bridge. It was highly instructive.

I didn’t drive the car – no one did, although it was Nissan’s engineer behind the wheel at all times. Several hacks returned from the experience pronouncing it “amazing”, but that seemed entirely the wrong description. The point was that it felt eerily normal, like going for a spin with a capable but disciplined and pedantic older driver who obeyed every speed limit to the letter and was never tempted to ‘take a line’ through a corner.

Nissan engineers see three levels of hands-off autonomy, but only the third (which they will offer from 2020) requires less than the driver’s full attention to the road. I can seea clear case for the first two levels, but I’m doubtful that our legal system could cope with a driver abandoning responsibility for control of his car to the machine itself.