Err, why is it illegal? They're more than fast enough to keep up with bike traffic in the city, especially if there are dedicated lanes.

Basically, the laws say that your vehicle must be licensed to be used on a road unless it’s a bicycle/pedal assist bike/a few other categories, and there’s no mechanism for licensing some of the newer transport options. The laws also say that a vehicle can’t be used on the pavement at all, so there’s no way they can be used on a public road at all.

And have you ever seen a picture of most British cities - there’s barely enough room for cars and pedestrians sometimes, never mind a whole separate lane for cyclists/etc.