Winston Silcott, who was wrongly accused of murdering a policeman during riots in north London in 1985, has been released from prison, the BBC has learned.
In 1991 Winston Silcott was cleared of murdering Pc Blakelock
Although Silcott was cleared of Pc Keith Blakelock's murder at the Court of Appeal in 1991, he has served 17 years for killing boxer Anthony Smith.
He stabbed the 24-year-old to death in a fight at a party in east London, but Silcott has always claimed he was acting in self-defence.
His solicitors Bindman and Partners have pointed out that his original sentence came with a 14-year tariff and he has now served more than 17.
It was announced last week that ministers and the Lord Chief Justice Lord Woolf had approved a parole board decision that Silcott was no danger to the public.
The BBC has learned that the 43-year-old walked free from Blantyre House open prison on Friday on a temporary licence.
He will be officially freed on life licence on Tuesday, which means he will be sent back to jail if he commits another crime.
He was due to return to Tottenham and will have to follow strict licence conditions for the rest of his life.
He is expected to take part in community work to steer young people away from crime.
Pc Blakelock was hacked to death by a mob during the Broadwater Farm riots in Tottenham, north London, in 1985.
Silcott was accused of being part of the mob while he was on bail awaiting trial for Mr Smith's murder.
But six years later he was cleared by the Court of Appeal as the conviction was seen as unsafe because of tainted police evidence.
Silcott was awarded £17,000 compensation by the home secretary for his wrongful conviction in the Blakelock case.
In 1999 he received a further £50,000 from the Metropolitan Police in settlement of a civil claim.
Pc Blakelock's widow Elizabeth Johnson, who has since remarried, said last week: "I do believe that guilty people will be brought to justice and we will see people being punished for what they did to Keith."