One of these in Gunners Park, Shoebury.
http://www.greyp.com/gallery
Very not legal - goes up to 70kph, apparently, and the website claims a battery range of 120km on an 80 minute charge.
It's got a 250W mode, but who's going to use that? TBH, I'm not sure what the legality of switchable limiting actually is. On one hand, it makes sense for a powerful off-road bike to have a way to easily make it legal. On the other, anything that doesn't involve unplug-the-battery or plug-in-a-laptop-and-reflash-the-firmware levels of faff is too easy to do while riding along.
I'd expect more than 120km from a bicycle with a 1.5kWh battery at legal speeds. Ah, there's a graph that suggests that's with knobbly tyres fitted, and it'll do a bit more on road tyres.
Zoinks! The Blue Thunder model appears to have twin front discs – that's more than most small motorbikes!
I, for one, would want a 48kg mountain bike to have as much braking as it possibly could!