to using sticky lumps of chewing gum, double-sided tape or Blu-Tack to cure what became known as the "RAM pack wobble" problem. The ZX Printer was a tiny spark printer that used two electrically charged styli to burn away the surface of aluminium-coated paper to reveal the black underlay. It worked reasonably well at first but its output deteriorated rapidly after a time. Many non-Sinclair peripherals aimed to remedy the ZX81's flaws and provide many new capabilities. These included RAM packs providing up to 64 KB of extra memory and promising to "fit snugly ... giving a firm connection" to the computer, typewriter-style keyboards, more advanced printers and sound generators, and even a hard disk interface, which Clive Sinclair thought was "quite overgilding the lily". A wide range of software was also published. Within only a year of the ZX81's launch, around 200 independent companies had been established to manufacture and sell Sinclair-compatible hardware. The people behind the ZX81 cottage industry were very often not computer professionals but were, as the Financial Times noted, "school teachers, civil servants, electrical engineers and technicians [who] have set up small operations in their own time". 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. Tens of thousands, mostly youths, came from around Britain, and the police had to control the crowd. They queued for three hours around the hall, with a group of 50 entering as another group left. About 12,000 entered 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, with the 14th ZX Microfair at Alexandra Palace in November 1984, still organised by Johnstone. Thousands of ZX81 programs were published, either as type-in programs or as ready-made applications that