A Commons committee has heard that Mohammed Ahmed Mohamed, who escaped from a mosque in West London, was involved in fighting, attack planning and recruiting for Al Shabab in Somalia.
The Home Affairs Committee is hearing evidence from David Anderson, the independent reviewer of terror laws. Anderson says Terrorism Prevention and Investigation Measures are not a foolproof way of keeping the population safe, adding:
"I'm troubled by the fact that there are cases which can't be prosecuted at all."
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Mayor Sadiq Khan urged Londoners to join him at 6pm in Trafalgar Square.
Pictures of today's events unfolding following a major security incident at the Houses of Parliament.