Sky News' Martin Brunt goes on the trail of Ali Harbi Ali, the 25-year-old main suspect in the killing of Sir David Amess.

With a backpack across his right shoulder he was seen wearing a green parka jacket and spectacles, with his hand in his left pocket.

Police are investigating Ali's movements in the hours leading up to the attack and are looking into whether he boarded a train at Gospel Oak station to travel to Leigh-on-Sea, Essex.

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