In 1934, Lonsdale returned to work with Bragg at the Royal Institution as a researcher. She was awarded a DSc from University College London in 1936 while at the Royal Institution. In addition to discovering the structure of benzene and hexachlorobenzene, Lonsdale worked on the synthesis of diamonds. She was a pioneer in the use of X-rays to study crystals. Lonsdale was one of the first two women elected a Fellow of the Royal Society (FRS) in 1945 (the other was the biochemist Marjory Stephenson).