Sinclair's third computer, the ZX81, was not "just another product" but became a veritable phenomenon. By modern standards it is laughably primitive: only 1K of memory, no colour or sound, touch-sensitive keyboard... but back in 1981 the idea that a complete, working computer could be bought off-the-shelf for under £100 was almost unheard of. It sold millions, virtually created the British home computer market and made Sinclair a millionaire.