Ediswan factory office block, Ponders End

The former Ediswan factory general office block of 1890, at Ponders End, occupies part of a site associated with Sir Joseph Swan (1828-1914), inventor of the incandescent electric lamp, Sir James Dewar (1842-1923), inventor of the vacuum flask, and Professor Ambrose Fleming (1849-1945), inventor of the diode radio valve in 1904, which marks the birth of the electronic technological revolution. Britain’s first radio valve and television cathode ray tube factories were opened here, in 1916 and 1936 respectively. This building is not listed, despite the site’s historical importance.