Training in crystallography
Born Kathleen Yardley, she graduated in physics from Bedford College, London, in 1922. William Henry Bragg, impressed by her examination results, invited her to join his research team. Her physics training led into X-ray crystallography, using diffraction measurements and calculations to investigate arrangements of atoms.
The benzene ring and academic appointments
Her crystallographic work in 1929 established that the benzene ring was a flat hexagon, providing experimental evidence about organic molecular structure. In 1945 she and Marjory Stephenson became the first women elected Fellows of the Royal Society. UCL appointed her professor in 1949, and she retired in 1968.
Pacifism and prison reform
A Quaker and pacifist, Lonsdale refused to register for civil-defence duties during the Second World War and spent a month in Holloway Prison. The experience led to sustained work for prison reform. She also campaigned for disarmament and peace, arguing that scientists should help the public understand facts and the social uses of science.