The law allows any heavy ebike to travel any speed downhill,with no restrictions (my old sakura really flew downhill,at 40 kg down a hill it hit 40mph no problem,but stopping it was pretty poor ,uphill it was very slow,i can now travel pretty fast up hills,but much slower down hills,with less weight and better brakes i can stop quicker,my old sakura was and still is classed as fully legal,because i can now travel faster uphill and above 15mph but not by much without assistance my bike is not legal,even though i could stop much sooner,especially downhill due to lower weight less speed and better brakes,i can understand restricting to 15mph, but a bike should still be able to hit close to 15mph uphill ,there is no point restricting uphill speed or power output up hills,when there is far less stopping distance.