A man has been questioned over the murder of Pc Keith Blakelock, who was killed 20 years ago during the Broadwater Farm riots in north London.
Pc Blakelock was murdered on the Broadwater Farm estate
The arrest was made after Scotland Yard and Pc Blakelock's widow renewed appeals for information last week on the anniversary of the killing.
The man, from Enfield, north London, was later released on bail.
Pc Blakelock died during the 1985 riot, sparked by the death of a woman who collapsed while police raided her home.
He was attacked with a number of weapons, including knives and machetes when he and a colleague went to the estate to protect firefighters.
Winston Silcott, Mark Braithwaite and Engin Raghip were convicted of the killing in 1987 but were later cleared on appeal.
A new murder investigation began in 2003 and was followed by the excavation of a back garden in Tottenham last year.
Pc Blakelock's widow, Elizabeth Johnson, said last week that not knowing who had killed her husband had made the last 20 years "extremely hard".
Detectives think there are people who are shielding the killer or killers, and last week urged them to come forward.
They also released images of the policeman's blood-stained overalls, with tape marks outlining the number of wounds inflicted upon him.
Detective Superintendent John Sweeney said: "Since our appeal last week on the 20th anniversary of the murder, we have had a number of valuable calls from the public that have identified useful lines of inquiry."
"We remain committed to dealing with this investigation as sensitively as possible."