Triode were invented, Philipp Lenard used the principle of grid control while conducting photoelectric experiments in 1902. The first vacuum tube used in radio was the thermionic diode or Fleming valve, invented by John Ambrose Fleming in 1904 as a detector for radio receivers. It was an evacuated glass bulb containing two electrodes, a heated filament and a plate (anode). Triodes came about in 1906 when American engineer Lee De Forest and Austrian physicist Robert von Lieben independently patented tubes that added a third electrode, a grid, between the filament and plate to control current. Von Lieben's partially-evacuated three-element tube, patented
Owen Williams (engineer) excelled in mathematics. He was apprenticed to the Electrical Tramways Co. in London in 1907 and at the same time did an engineering degree at the University of London. In 1912 Williams assumed a position as engineer and designer with the Trussed Concrete Company. Seven years later, he started his own consulting firm, Williams Concrete Structures. He was then appointed chief consulting civil engineer to the British Empire Exhibition which included the old Wembley Stadium. The commission also included the Palace of Industry building in Brent, the first building in the United Kingdom to use concrete as the exterior. The