Two teenagers, aged 14 and 15 have been charged with the murder of 85-year-old Paula Castle. She died of a head injury after her handbag was stolen in Greenford on Monday.
The two have also been charged with robbery, and will appear in court in Uxbridge later today.
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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.