A series of marches by a right-wing group has been banned amid fears of violence on the streets.
Policing minister Damian Green agreed to the Metropolitan Police request for the ban to stop serious public disorder ahead of marches by the English Defence League in Waltham Forest, north-east London, and three surrounding boroughs.
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The entertainer was held for the murder of Stuart Lubbock, who was found dead in his swimming pool in 2001, but never charged.
Although the diamond was believed to be cut in the 19th Century, its history and how it arrived at the car boot sale is unknown.
The former entertainer, who was released from prison on Friday, is accused of indecently assaulting three women in the 70s and 80s.