Which King's College physicist showed Watson an X-ray image of DNA in January 1953?

The King’s College physicist who showed Watson an X-ray image of DNA in January 1953 was Maurice Wilkins.

Wilkins showed James Watson a high-quality image of the B-form of DNA, now known as Photo 51. The photograph had been made in 1952 by Raymond Gosling while working with Rosalind Franklin at King’s College London. Its characteristic X-shaped diffraction pattern strongly indicated a helical structure and gave Watson and Francis Crick crucial evidence for their model.

The episode is historically important but often oversimplified. Wilkins did not take Photo 51 himself, and Franklin was the scientist whose experimental work and analysis underlay the image. Wilkins obtained access to it during the reorganization of responsibilities at the laboratory and showed it to Watson without Franklin’s knowledge at the time, a decision later examined in debates about credit and scientific conduct.

Watson and Crick combined the image with other measurements and chemical constraints rather than relying on one photograph alone. Their double-helix paper appeared in Nature in April 1953, followed in the same issue by papers from Wilkins’s group and from Franklin and Gosling.