The parents of the murdered teenager Jimmy Mizen are to receive an MBE for their work with young people at Buckingham Palace later.
Margaret and Barry Mizen worked tirelessly to raise young people's awareness of the consequences of violent crime, following the death of their son in 2008.
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David Cameron said the Met proved it can "do more with less" and declined to criticise the Mayor of London for his water cannon spend.
A group of disabled activists threw toys and balls at him as he entered the conference.
A wet start to the week and the unsettled weather is set to continue over the next few days.