||Following the invention of the fluorescent tube by GE of America and its exhibition at New York's World Fair in 1938, the rest of the world was quick to adopt this technology. Osram-GEC in England was the second company to offer a fluorescent lamp, but because of wartime restrictions the design had to be modified from the original GE format to suit the materials which were available here at the time. BTH, Philips and Crompton later commenced fluorescent production in the UK according to the Osram design.
The standard bi-pin cap was introduced with the GE lamp, but it was intolerable for Britain to devote energy to commencing production of this new cap and lampholders during the war, so the first British tubes employed ordinary BC bayonet caps as found on filament lamps. Secondly it was deemed wasteful to design and set up production of a new choke which was required for the 4-foot 40W tubes gaining rapid acceptance in the USA. The smallest choke in UK production at the time was the 80W MB mercury lamp ballast, and it was therefore decided to design a fluorescent tube which could run on this control gear.
Thus the first British tubes were rated 80W, had ordinary BC caps and the tube length was increased to 5 feet. An 8-foot tube with BC caps was later made available to run on the 125W mercury ballasts. The high electrical loading of these tubes made them somewhat inefficient though, and after the war when effort could be devoted to creating new ballasts, these lamps were down-rated to 65W and 85W and the bi-pin cap was introduced as well. But in view of the vast quantity of BC luminaires installed during the war these lamps remained in production until the late 1980s.