Linus Pauling showed evidence for a helix and planar base stacking along the helix axis. Early in 1953 Watson and Crick proposed a correct structure for the DNA double helix. Pauling later cited several reasons to explain how he had been misled about the structure of DNA, among them misleading density data and the lack of high quality X-ray diffraction photographs. During the time Pauling was researching the problem, Rosalind Franklin in England was creating the world's best images. They were key to Watson's and Crick's success. Pauling did not see them before devising his mistaken DNA structure, although his assistant Robert
Francis Crick Britain as planned in May 1952. As it was, his political activities caused his travel to be restricted by the United States government and he did not visit the UK until later, at which point he met none of the DNA researchers in England. At any rate he was preoccupied with proteins at the time, not DNA. Watson and Crick were not officially working on DNA. Crick was writing his Ph.D. thesis; Watson also had other work such as trying to obtain crystals of myoglobin for X-ray diffraction experiments. In 1952, Watson performed X-ray diffraction on tobacco mosaic virus and