 Watson and Crick collaborated to build a model of the double helical structure of DNA, with its two helical strands held together by hydrogen-bonded base pairs (Olby 1994). They made extensive use of data from x-ray crystallography work on DNA by Maurice Wilkins and Rosalind Franklin at King’s College, London, appallingly without Franklin’s permission or even knowledge (Maddox 2002), Crick’s theoretical work on crystallography (Crick 1988), and the model building techniques pioneered by Pauling (de Chadarevian 2002; Judson 1996; Olby 1970, 1994, 2009).