Herbert Cecil Booth, the inventor of the vacuum cleaner, well knew the vital importance of reversal to creative thinking. In other words, looking at something and then turning it on its head. What if people walked on their hands instead of their feet? What if elephants were the size of mice and vice versa?

  Booth decided to 'suck, not blow' when in 1901 he saw a demonstration of an American machine for cleaning train carriages which used a high pressure air jet to blow the dust out of fabrics. It later occurred to Booth that it might be a better idea to suck the dust up and so the vacuum cleaner was born.