In 1916, two years into World War I, a group of artists holed up in a Zurich cabaret decided that if the world outside I had gone mad, art didn’t owe anyone order either. So they made a mess of it, on purpose. They stuck newspaper clippings together to make collages, pulled random words from a hat and called it poetry and, in one famous case, signed a urinal and put it in a gallery. They called it Dada, a name they picked at random from a dictionary, which tells you most of what you…

