Sir John Ambrose Fleming, English physicist and electrical engineer, 1904.
© Science Museum / Science & Society Picture Library
Photograph. Profesor of Electrical Engineering at University College, London, between 1885 and 1926, Fleming (1849-1945) invented the thermionic valve and was a pioneer in the application of electricity to lighting and heating on a large scale. He was also instrumental in the development of radio telegraphy and telephony.