Hoogstraten: The enforcer

But the jury was not told of his violent history as an armed robber or that he was released from prison just three months before he brutally murdered Mohammed Raja.

The court heard he was close to his "millionaire friend" Nicholas Hoogstraten for 30 years and was called upon to deal with difficult tenants.

But the jury did not hear Hoogstraten's young girlfriend Tanaka Sali swear on oath that Knapp was introduced to her as the tycoon's "hitman" because she later retracted her statement.

The jury heard Hoogstraten was close to Knapp's mother, who lives in a cottage on his High Cross Estate.

But Hoogstraten maintained in later years he avoided Knapp junior because of his heroin addiction.

However, he was forced to admit writing five letters to Knapp between October 1998 and March 1999 while Knapp was in jail.

These were intercepted by guards but, in order to avoid prejudicing the murder trial, no evidence about their contents was revealed.

Knapp was portrayed as the link between David Croke, whose blood was found at the scene of the murder, and Hoogstraten, who had the motive.

He was a key suspect because of his known links with Hoogstraten, whom he met in prison in the Seventies.

He was ruled out as the assassin who spilled blood on Mr Raja's doorframe after police took a DNA sample from his mother.

There was no forensic evidence to convict Knapp - although a fertiliser bag in the burnt-out getaway van matched one found in his mother's garage.

However, mobile phone records tracked Knapp's movements around the M25 on the day of the murder.

These proved that, after murdering Mr Raja in Sutton, Surrey, he and Croke drove eastwards around the M25 London orbital to Crayford, Kent.

Knapp often visited friend and fellow drug user Doreen Tong in Crayford and the pair would go to London together to her dealers.

After the murder, he and Croke arrived with burns from torching the getaway van. That was the only occasion Miss Tong saw the pair together.

Another piece of the jigsaw fell into place when police examined the mobile phone records.

Between Knapp and Croke being released from prison in the spring of 1999 and the day of the murder, there were 27 mobile phone calls between them. They did not phone each other again after July 2.

In 2000, Knapp left the UK for the Republic of Ireland with his wife Jackie after telling Miss Tong he had been "stitched up" by his millionaire pal.

He later told police his main reason for leaving was to kick his heroin addiction.

Police seized a series of letters Knapp had written from Ireland to his mother in August and September 2000. In them, he asked for her forgiveness and described being under "serious pressure".

Of his decision to leave, he wrote: "People told me to keep well away because there was a letter on my doormat from detectives wanting to interview me for a murder. The information I have is about nil or less."

In 1979, Knapp's mother, Sylvia, and his late father, Arthur, moved on to Hoogstraten's High Cross estate.

Knapp worked with Hoogstraten intermittently over the years, mainly to deal with "awkward" tenants.

However, the jury was not told of his other activities during this period.

In March 1974, he was sentenced to five years in prison for possession of a shotgun and revolver without licences, possession of ammunition and attempted robbery.

In June 1979, he was convicted of theft of a cheque, forgery and absconding from bail. He was sentenced to two years in prison.

The following year, he was sentenced to three years for two house burglaries.

In May 1987, Knapp was sentenced to 13 years in prison for hijacking a post office van containing £100,000.

Just seven years later he was free, however, and held up a jewellery shop.

He was convicted of armed robbery and using a firearm to resist arrest and sentenced to 12 years' imprisonment. He was released in April 1999.

During this time, he also changed his name at least twice, from Robert Knapp to Robert Pierson and back.

In the summer of 1999, Hoogstraten moved him into a flat he owned at Framfield Road, Uckfield, to be near his frail mother.

The prosecution maintained Knapp was an "enforcer" for the tycoon. This was backed by the evidence of Hoogstraten's architect Anthony Browne about how difficult tenants might be handled.

He told the court: "Robert was a big man, a forceful character, and we could use him if he so agreed to deal with violent people."

Mr Browne described a cooling in the relationship between Knapp and Hoogstraten over the years but said Hoogstraten planned to move Knapp into the Boat House being built on the High Cross Estate.

This was prior to Knapp's relocation to Ireland.

Croke, of Bolney Road, Moulsecoomb, Brighton, was arrested in February 2001 and, following Hoogstraten's arrest in July 2001, Knapp saw his name in the newspapers being linked with Mr Raja's murder.

At the time, police were considering starting extradition proceedings against him.

Because of the length of time that could have taken, the Crown Prosecution Service was ready to run the trial with just Hoogstraten and Croke. But in September 2001, Knapp returned to Britain. He told police he felt he had no choice.

He was arrested in Crayford.

In interviews, he refused to discuss his relationships with any third parties, including Hoogstraten, Croke and Miss Tong.

However, he did question why the fact that DNA matching that of Croke's found at the scene had anything to do with Hoogstraten.

He said: "If David Croke is involved in this killing, it is a presumption on your part that it has anything to do with Nicholas van Hoogstraten or myself."

A presumption that was so obviously true.