I believe that the use of only regenerative braking is, as I've said before, not adequate. My Vectrix's regen braking is wonderful, and I use it as my primary braking, when I'm moving. But if I didn't have the friction brakes, I wouldn't be riding it at all; I couldn't safely keep it from rolling when stopped on any slope.
I've read the Lightning literature, and I'm just not buying their assertions that they are using only regen braking. They've got to be using something additional, and friction braking is the obvious choice. I personally don't have a problem with it if they are, except to point out that those wheel hubs are getting crowded with plenty of complexity.
What are the regulations concerning automobile braking systems in the UK? Are we just a bunch of Nervous Nellies here on this side of the pond, and the UK auto manufacturers are using all sorts of new, exciting, innovative braking systems?