 The ZX81 's popularity was publicly demonstrated in January 1982 when civil servant Mike Johnstone organised a " ZX Microfair " at Westminster Central Hall . Seventy exhibitors set up stalls with only a few hundred visitors expected in a hall with a capacity of 650 people . More than 12 @,@ 000 people came and the police had to control the crowd . Thousands , many of whom had travelled long distances , queued outside for up to three hours to get into the hall ; Clarke , who was only able to enter after identifying himself as a journalist , wrote that " no one knows how many gave up in despair " . The exhibitors sold thousands of pounds ' worth of software and hardware " as fast as three pairs of hands on each stall could hand them over and stuff the fivers into improvised overflowing cash boxes " , he added . The fair also showed Sinclair Research 's relatively unimportant role in the computer 's success , with only small crowds at its booth compared to the " rugby scrum " elsewhere . By August 1983 seven more ZX Microfairs were held . 
