Nicholas Jacobs, 44, is due to appear at the Old Bailey on Friday after being charged with the 1985 murder of PC Keith Blakelock during riots in Tottenham, north London.
Jacobs is accused of killing the 40-year-old officer, who was stabbed as he tried to protect firefighters as they tackled a blaze at a supermarket during the height of the unrest in Tottenham.
Prosecutors announced on Tuesday that Jacobs had been charged over Pc Blakelock's death.
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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.