A key witness in the PC Keith Blakelock murder trial has denied he "fitted up" the defendant to receive a £5,000 reward from police.

Using the pseudonym John Brown and with his voice distorted by a modulator to protect his identity, the witness told the Old Bailey that he saw the killing on the estate in Tottenham, north London, on October 6, 1985.

Mr Brown claimed to have seen Nicky Jacobs, 45, stabbing PC Blakelock with a machete between two and four times, while he himself had kicked the officer up to ten times.

He admitted he had received £5,000 and help from the Metropolitan Police with his rent and telephone and internet bills for his evidence, but said he had not come forward for the money.

In cross-examination, defence barrister Courtenay Griffiths accused him of "joining heads together" with another key witness, referred to in court as Rhodes Levin, to point the finger at an "easy target".

Mr Griffiths asked: "Your motivation for coming forward to give this lying account is money, pure and simple, isn't it?"

Mr Brown replied: "No, definitely not."

The defence asked: "You and Rhodes Levin joined your heads together to fit up Nicky Jacobs, didn't you?"

Mr Brown replied: "That's rubbish, I'm sorry."

He was also asked: "And you did it for the money?"

He replied: "No, that's not true."

The court heard that Mr Brown had not mentioned Jacobs in his first statement given to police in January 1986.

After pleading guilty to affray and burglary in connection with the riots, he then gave a statement in July that year placing Jacobs at the scene.

Mr Brown told the court that he was 18 or 19 at the time of the riots, while Jacobs was 16.

After the riots, Mr Brown gave evidence against Jacobs at a trial against him for affray in November 1986.

Mr Griffths asked the witness if he had decided to place the defendant at the scene " one, because he was young; two, because he posed no threat to you; and three, you quite wrongly thought that he had been charged with murder."

Mr Brown disagreed.

When a fresh investigation into PC Blakelock's death got under way in 1992, suspects were separated into "kickers and stabbers".

Those who had not used weapons - "kickers" - were given immunity from prosecution as police tried to identify who had stabbed the officer to death.

It was then that Mr Brown gave evidence claiming for the first time that he had seen Jacobs use a weapon, the court heard.

Mr Griffiths asked the witness if police officers had visited him at this home in June 1993 and told him that, in order for there to be a "realistic prospect of prosecution", three or four witnesses would need to come forward.

He also asked if Mr Brown had then put his cousin up as an eyewitness in order to get the reward.

While he acknowledged that police had visited him, Mr Brown said he "totally disagreed" with the claim.

Earlier, the witness claimed he saw PC Blakelock curl up into a ball and scream "help, help, help" as the mob hacked him to death.

He said he saw a sword, a 15-inch dagger and the machete allegedly wielded by Jacobs during the "frantic" attack.

Mr Brown said the machete had a 12-inch blade and Jacobs was "stabbing up and down" with it during the attack.

He also said it was "common knowledge" ahead of the riots that there was going to be trouble.

Mr Brown said he had allegedly heard others say that Jacobs was going round claiming he was going to "give an officer a hiding if he got the opportunity, or do some damage".

Asked why he himself had kicked PC Blakelock, 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."

Mr Griffiths said: "I'm going to suggest to you at no stage during this initial interview did you mention the name Nicky Jacobs to the police, did you?"

The witness said: "I do not think so?"

Asked: "were you frightened of Nicky Jacobs then," the witness replied: "Yes, I was frightened to death - Nicky Jacobs, consequences, people coming after me, yes."

Mr Griffiths read out an extract from his interview in which he gave his opinion on the reasons for the riots, saying: "Well to me I'm not being racialist (sic) the black people always got a chip on their shoulder and the police were always picking them off so they were out to get the police..."

The witness was also quizzed about a police interview in January 1989 in which he lied about his involvement.

The barrister asked his reasons for lying, to which he replied: "I probably said I was further away than what I was because I was scared of being charged, I suppose."

He also said he was scared for his own welfare and that of his family.

Asked if anyone had attacked him before the interview, the witness said: "No."

The court heard that in 1986, the witness named three friends, including members of his gang, as being close to PC Blakelock during the attack.

Mr Griffiths asked: "You name three mates but not Nicky Jacobs, why?"

He replied: "I just did not come out with the full details."

Mr Brown initially told police his "eyesight is very bad" because he was wearing his glasses on the night of the riots.

But that was not true, he said: "I do not wear glasses. I have never worn glasses all my life."

Jacobs denies murder. The case continues.