It’s extraordinary that it took civilisation so very long to discover the benefits of putting little wheels on suitcases. We knew how to fly before we realised it was no longer necessary to huff-and-puff baggage by hand.

Even odder, steam and electricity were well understood before anyone got around to developing the ingeniously simple pedal-and-crank mechanism, an invention of decisive importance, which turned the ludicrous, wobbly old hobbyhorse into today’s smooth and sensible bicycle.