article_snippet: Around 600 Britons, many of 600 Britons teenagers or young adults, are believed to have joined IS since 2013.
article_snippet: Several children have already travelled to Syria to join the extremist group, including four girls from Bethnal Green academy in east London.
article_snippet: Around 600 Britons, many of 600 Britons teenagers or young adults, are believed to have joined IS since 2013 (file picture) 600 Britons paid cash for direct flights to Istanbul before crossing the border to Syria.
highlights_snippet: About 600 Britons are believed to have joined Islamic State since 2013 .