PC Keith Blakelock curled up in a ball and screamed for help as a mob hacked him to death during the Broadwater Farm riots, an eyewitness has told the Old Bailey.
Using the pseudonym John Brown and with his voice distorted by a modulator to protect his identity, the witness described how he saw the killing of the Sunderland officer on the estate in Tottenham, north London, on October 6 1985.
He explained that he had seen Nicky Jacobs, 45, stabbing Pc Blakelock with a machete between two and four times as the frenzied mob took part in a free for all.
Asked by Richard Whittam QC, for the prosecution, what the officer was doing during the attack, Mr Brown said: "What I saw, he was trying to curl up into a ball, I suppose to protect himself somehow."
"Did he say anything?" Mr Whittam asked.
"I just heard heard screams of 'help, help, help'," he replied.
Mr Brown, a former member of the Park Lane Boys gang, who accepted a caution for assaulting his partner in 2010, said Jacobs used a machete with a 12ins blade during the attack.
"He was attacking the officer and hit him with a couple of blows on his body, stabbing up and down with the machete," he said.
Afterwards Mr Brown saw a gash on the officer's neck and blows on his body, he said.
He told the jury that he himself had kicked the officer some ten times after he went to the ground.
Asked why, he said: "Looking back on it I don't know.
"It was the excitement of the situation, I just rushed forward and kicked him about ten times."
The witness said he had been paid a £5,000 reward by the police after giving a statement during a renewed police investigation into the killing in 1993.
Mr Brown also said it was "common knowledge" ahead of the riots that there was going to be trouble.
He told the jury that he had heard others say that Jacobs was going round saying he was going to "give an officer a hiding if he got the opportunity, or do some damage".
Jacobs denies murder.