Before electronic computers were available at CERN, a Dutchman called Willem "Wim" Klein performed astonishing feats of mental arithmetic to help his colleagues with their calculations.

Klein was born in Amsterdam in the Netherlands on 4 December 1912. He first displayed his mathematical talents in circuses around Europe. He joined CERN's Theory Division in 1958, where he was in considerable demand as a calculator in the days before the first electronic computers.