model, and certainly had written them before she knew of their work. On 8 July 1953 she modified one of these "in proof" Acta articles, "in light of recent work" by the King's and Cambridge research teams. The third draft paper was on the B form of DNA, dated 17 March 1953, which was discovered years later amongst her papers, by Franklin's Birkbeck colleague, Aaron Klug. He then published an evaluation of the draft's close correlation with the third of the original trio of 25 April 1953 Nature DNA articles. Klug designed this paper to complement the first article he had written defending Franklin's significant contribution to DNA structure. He had written this first article in response to the incomplete picture of Franklin's work depicted in Watson's 1968 memoir, The Double Helix. As vividly described in The Double Helix, on 30 January 1953, Watson travelled to King's carrying a preprint of Linus Pauling's incorrect proposal for DNA structure. Since Wilkins was not in his office, Watson went to Franklin's lab with his urgent message that they should all collaborate before Pauling discovered his error. The unimpressed Franklin became angry when Watson suggested she did not know how to interpret her own data. Watson hastily retreated, backing into Wilkins who had been attracted by the commotion. Wilkins commiserated with his harried friend and then showed Watson Franklin's DNA X-ray image. Watson, in turn, showed Wilkins a prepublication manuscript by Pauling and Corey, which contained a DNA structure remarkably like their first incorrect model. DNA research In February 1953, James Watson and Francis Crick of the Cavendish Laboratory in Cambridge University had started to build a molecular model of the B form of DNA using data similar to that available to both teams at King's. Much of their data was derived directly from research done at King's by Wilkins and Franklin. Franklin's research was completed by February 1953, ahead of her move to Birkbeck, and her data was critical. Model building had been applied successfully in the elucidation of the structure of the alpha helix by Linus Pauling in 1951, but Franklin was opposed to prematurely building theoretical models, until sufficient data were obtained to properly guide the model building. She took the view that building a model was to be undertaken only after enough of the structure was known. Ever cautious, she wanted to eliminate misleading possibilities. Photographs of her Birkbeck work table show that she routinely used small molecular models, although certainly not ones on the grand scale successfully used at Cambridge for DNA. In the middle of February 1953, Crick's thesis advisor, Max Perutz, gave Crick a copy of a report written for a Medical Research Council biophysics committee visit to King's in December 1952, containing many of Franklin's crystallographic calculations. Since Franklin had decided to transfer to Birkbeck College and Randall had insisted that all DNA work must stay at King's, Wilkins was given copies of Franklin's diffraction photographs by Gosling. By 28 February 1953, Watson and Crick felt they had solved the problem enough for Crick to proclaim (in the local pub) that they had "found the secret of life". However, they knew they must complete their model before they could be certain. Watson and Crick finished building their model on 7 March 1953, one day before they received a letter from Wilkins stating that Franklin was finally leaving and they could put "all hands to the pump". This was also one day after Franklin's two A-DNA papers had reached Acta Crystallographica. Wilkins came to see the model the following week, according to Franklin's biographer Brenda Maddox