…not a good idea. Five to seven years for making one is a bit excessive, even by British standards; but I can see where the English might be a bit leery of letting people wander around with flame-based tailgate-prevention devices. We don’t really want Car Wars
That being said, and as I commented to @eddiebear, if this had happened when Charles II was king the inventor would have gotten an earldom out of it. Err, assuming that he didn’t get a dukedom for the scooter.