“More than 700 Britons are thought to have traveled to Syria and over a half have since returned home where they now pose a significant terrorism threat, British police said on Thursday. Mark Rowley, the lead officer on counter-terrorism, also said there had been a record 338 arrests for terrorism-related offences last year, up by a third from 2013, with almost a half related to the conflict in Syria.”
Source: Police: Over 700 Britons Traveled to Syria, Half Now Home