The Metropolitan Police has told ITV News that 50 people have been temporarily detained as a result of the 'critical mass' procession.
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The shadow home secretary, 63, said she worked in the Home Office for nearly three years when she was a trainee.
Home Secretary Amber Rudd has attacked Labour's capabilities to effectively deal with any future terrorism threats facing the UK.
Tori Lee Castillo, 39, has been arrested on suspicion of child abuse.