There have been claims that the justice system is failing people with mental illness, after research found they are three times more likely to be victims of crime.
Research by London universities found people with mental illness often felt they weren't believed when they reported crimes to police. Some were even left feeling they were to blame.
Our Senior Correspondent Ronke Phillips reports.
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In a wide-ranging Peston on Sunday interview, he said Parliament security needs reviewing and the PM's counter-terror strategy is flawed.
The terror attack carried out by Khalid Masood at Westminster that left four people dead lasted less than two minutes say police.
Two knives were found at the scene in Islington, North London, and the suspects fled on foot before being arrested.