So, really, Uncle Clive's 21st century try was only slightly ahead of his time?
www.envirotech.com.co This one is rather expensive, but there are some interesting performance electric scooters/bikes (800w-1Kw/h) now coming onto the market for not a great deal more than a half-decent push bike. Unfortunately it's highly likely that they aren't at all road legal. Want, anyway! I like the off-road bit here at about 4:00, you wouldn't get away with that on a noisy motorbike. It rather looks like the braking system puts some energy back into the battery.