Thomas Lewis. Portrait of Sir Thomas Lewis (1881- 1945), Welsh cadiologist and clinical scientist. He is standing in the laboratory in Leiden where Einthoven had invented the electrocardiograph (ECG). Cardiff-born Lewis worked from 1902 until his death at University College Hospital in London. Gaining an interest in cardiac physiology and diseases of the heart, Lewis was the first to master the use of the ECG and he established the basic parameters to interpret the ECG in health and diagnose disease. He fought for full-time clinical research posts and wrote textbooks on cardiology. He was knighted in 1921.