Ali Harbi Ali, 25, is being held by police on suspicion of murdering the veteran Conservative MP as he met with his Southend West constituents on Friday afternoon. Police and intelligence officials are said to be mystified about why the 69-year-old Tory politician was singled out for attack by a suspected Islamist extremist. Reports had initially suggested that Sir David, a devout Roman Catholic and prominent Brexiteer who was MP for Southend West, had been selected because of his political views or religion. Investigators now believe that there may have been no specific motive for the targeting of Sir David, and that the 69-year-old was stabbed to death because his alleged killer had succeeded in booking a face-to-face meeting with him at a church in Leigh-on-Sea on Friday. Last night former friends of Ali, a British national of Somali heritage who grew up in a three-bed terrace house in Croydon with his mother, two sisters and brother, claimed he was radicalised after watching YouTube videos of hate preacher Anjem Choudary.