[1] Bywaters studied at the Middlesex Hospital Medical School, graduating in 1933 with a gold medal and honours in pathology, and then worked as an assistant to pathologist Lionel Whitby.
When war broke out in 1939, Bywaters returned to Britain, but was not taken into the army because of kidney problems and instead took over Rheumatology at the British Postgraduate Medical School at Hammersmith Hospital.
Immediately after the discovery of the therapeutic effect of cortisone against rheumatic fever by Philip Showalter Hench and Edward Calvin Kendall he undertook clinical tests that confirmed this (participation in 1948).
Bywaters used his expertise as a pathologist for accurate characterization of rheumatic diseases and to develop new methods of treatment of juvenile chronic arthritis in children and adolescents.
In 1963 he received the Canada Gairdner International Award for his work studying rheumatoid arthritis, and he was made a Commander of the Order of the British Empire in 1975.