At last, mobility restored :. The new battery is connected to two of the jumble of wires sprouting from the controller (?). The black wire to the black terminal and the red wire, oh, you're there before me. Twist the throttle and the wheel goes round. Just like a real motor bike. The lights don't work and the application of the brakes doesn't disconnect power so riding isn't quite as idiot proof as I'd like... still, the wheels go round again. Pedalling motivates the motor as well. Quite pleased with myself. Juicy Lucy takes to the Cheshire lanes again.