Julie Shain of the Counter Extremism Project, told The Times: 'This incentivises people to search for these things and suggests it's normal to do so. 'In combination with the thousands of videos and pages calling for attacks on the West, it's incredibly dangerous.' Al-Awlaki spoke American English, and his sermons are widely available online.  His primary message was Muslims were 'under attack' and had 'a duty to carry out attacks on non-believers at home'.  Al-Awlaki lived in the UK between 2002 and 2004 and gave a series of lectures in London, warning people 'not to trust non-Muslims' and speaking of the 'rewards of martyrdom'.