A Mission Impossible-style memory stick that self-destructs its data if stolen has been developed by a Wallingford inventor. Norman Shaw, 57, of Market Place, designed and built the Security Guardian in a bid to help safeguard the 50 million items of personal data that go missing in Britain each year. The device automatically deletes files when lost or stolen and an inbuilt GPS tracking device can pinpoint its exact whereabouts anywhere in the world to within 30 yards.