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Steven Mitchell of Cheshire wants to prevent crowd trouble at flashpoint sports events by giving early warning if rival fans start to mix (GB 2380882). In Mitchell’s scheme, fans must wear radio tags on their wrist to gain entry to a sports stadium. There are two types of tag, which show as red and blue blips on a screen in the security centre. The screen is overlaid with a map of the stadium. If the screen shows red and blue clouds of blips at opposite ends of the pitch, there is no cause for alarm. If the colours start to mix it means a hot spot has formed, and security guards move in.