Britain's Prime Minister David Cameron (2nd L) walks to Parliament after leaving Number 10 Downing Street in London September 1, 2014. Cameron will announce new laws on Monday to try to stop radicalised Britons returning from Syria and Iraq launching attacks on British soil, after a video purportedly showed a London-accented man beheading a U.S. journalist. REUTERS/Luke MacGregor (BRITAIN - Tags: POLITICS CONFLICT MILITARY TPX IMAGES OF THE DAY)