And a man who was a teenager at the time of PC Keith Blakelock's death has been charged with the officer's murder during riots in North London in 1985.
44-year-old Nicholas Jacobs will appear in court tomorrow.
PC Blakelock was was stabbed to death as he tried to protect firefighters tackling a blaze at a supermarket at the hight of the unrest.
ITV News Reporter Ben Chapman reports.
PC Blakelock was a father of three and his family welcomed today's charge. In a brief statement, the family said:
Three men - Winston Silcot, Mark Braithwaite and Engin Raghip - were convicted of the police officer's murder in March 1987, but all three had their convictions quashed our and a half years later, after forensic tests on pages of interview records suggested they had been fabricated.
In 2003, Scotland Yard reopened the murder investigation after a judicial review indicated there were possible new lines of inquiry.
In 2010, 14 men were arrested in connection with PC Blakelock's death and the attempted murder of his colleague PC Richard Coombes, 9 were told in August 2011 that they would face no further action, and the rest except Jacobs have now been released.
PC Coombes told ITV he was quietly optimistic justice is a step closer this evening.