[2] This is the Society's principal prize, awarded biennially for an outstanding contribution of current importance in microbiology.

Robert Stephenson was a prominent figure in the local community, appointed as a Justice of the Peace and then Deputy Lieutenant of Cambridgeshire; he was also a chairman of the County Council.

As Stephenson did not find domestic science fulfilling, she was grateful when R. H. A. Plimmer, co-founder of the Biochemical Club (later Society), invited her to become a researcher in his laboratory at University College London.

Her studies of the intestine focused on the enzyme lactase, necessary for digestion of milk, and showed that it was inhibited by glucose but not galactose.

[4] After joining the British Red Cross Society, Stephenson ran hospital kitchens in France; later she became a Voluntary Aid Detachment (VAD) commandant in Salonica (Thessaloniki).

[6] The department had an unusually high proportion of women amongst its researchers, at 15 per cent, but it was still very rare for a woman to be offered a University appointment.

With Margaret Whetham and Juda Quastel, she developed the washed suspension technique, which had originated with Louis Pasteur, for extracting enzymes from bacteria.

With Leonard Stickland, she was the first to isolate a bacterial enzyme from the cell in 1928, when they obtained lactic dehydrogenase from Escherichia coli.

The Sex Disqualification (Removal) Act 1919 and a Privy Council ruling on the legal status of women in 1929 rendered these arguments obsolete.

Charles Harington nominated Stephenson and, after a ballot in which a large majority of Fellows voted to accept women, she was duly elected in 1945 together with Kathleen Lonsdale.

After the war the Rockefeller Foundation and the Medical Research Council funded a new laboratory at Cambridge (known as the "Bug Hut"), to which she moved in 1947.

[8] Also in 1947 she was finally recognised by the university for her many years of service; they appointed her as the first Reader in Chemical Microbiology, a permanent position.