>> Islamic State claims London's Westminster attacker is one of their own. But police believe British born Khalid Masood acted alone and that the motive for the 52 year old Islamic convert's rampage may never be understood. Deputy Assistant Commissioner Neil Basu says, there's no intelligence to suggest further attacks are planned and police remain determined to understand if Masood was a lone actor inspired by terrorist propaganda or if others encouraged, supported or directed him.
Four people died and a dozens more injured when Masood sped across Westminster's bridge in a car, mowing down pedestrians and running through the gates of the nearby parliamentary precinct where he fatally stabbed unarmed policeman, Keith Palmer, before being shot dead. Police raided properties and several areas of England after the attack, arresting 11 people.
Only one remained in custody on Saturday. Masood was no one to police but before launching the deadly attack, he was considered little serious threat showing up on the periphery of previous terrorism investigations, but then falling from the radar. He'd raked up a string of non terrorism related convictions.
His last, 14 years ago for possession of a knife. Police say even if he did act alone, they need to give as much explanation as possible to reassure Londoners, Basu said their investigation continues at pace.