As a small kid I remember having toy cars that you revved and then let go. I found great pleasure as those cars would race across the floor negotiating bumps in carpets and curious pets until they finally ran out of steam. Yelling with delight the revving process would begin again and off those cars would go negotiating new bumps and braver pets. When I got bored of those cars the cat got a clockwork mouse. The dog by then, had developed a taste for the bread the milkman left on people’s doorsteps and had swapped chasing toys for being chased by irate neighbours.