Security services have barred more than 200 foreign scientists from studying at British universities over the past four years, amid fears they could present a terrorist threat, a newspaper reported.The Guardian newspaper said the scientists were among more than 2,000 vetted after applying to universities to do postgraduate or post-doctoral research in fields such as chemistry, microbiology and biotechnology. The figures were released to the Guardian under the Freedom of Information Act as police continue to search for those linked to the London terror bombings on July 7.Full Story