The Sinclair ZX Spectrum
By far the most famous and successful of his many products, the ZX Spectrum earned Clive Sinclair a fortune, a knighthood for "services to British industry" and a lasting place in the national consciousness. Huge numbers of Spectrums were sold around the world, making it by some way the most successful British computer ever made. Sinclair's standing rose so high that in 1983 Margaret Thatcher personally presented a Spectrum to the Japanese Prime Minister as a symbol of British technological prowess (although this turned out to be more of a symbol of Thatcherite hubris).
The ZX Spectrum was the longest-lived Sinclair product, eventually appearing in seven distinct versions produced over a six-year period.
The Spectrum continued to sell into the early 1990s, but by about 1992 it had been squeezed out by the more advanced 16-bit computers and the cheap but more capable Sega and Nintendo games consoles.