Fleming was awarded the IRE Medal of Honor in 1933 for "the conspicuous part he played in introducing physical and engineering principles into the radio art". He is known for inventing the first thermionic valve or vacuum tube the diode then called the kenotron in 1904. In 1899 Fleming became Scientific Advisor to the Marconi Company and soon after began work on the designing the power plant to enable the Marconi Company to transmit across the Atlantic.
Having no children he bequeathed much of his estate to Christian charities especially those that helped the poor. He was an accompliJohn Ambrose Flemingd photographer and in addition he painted watercolours and enjoyed climbing in the Alps. He was a devout Christian and preached on one occasion at St Martin-in-the-Fields in London on the topic of evidence for the resurrection.