David Austin, formerly of New Addington in south London, was serving a life sentence for the high-profile 2004 murder of Charlie Butler in Dagenham.
A Prison and Probation Ombudsman report has revealed that Austin died on December 1 last year of a thrombotic stroke.
Mr Butler, who owned a wheelclamping company and was said to have a history of dishonestly, was shot near his home in Dagenham in October 2004.
He remained alive for nine months before he eventually died of his injuries.
The case remained unsolved until 2006 when the CCTV footage taken from a CCTV camera outside Mr Butler’s home was aired on BBC’s Crimewatch.
Mr Butler could be seen getting out of his Range Rover late at night when another man suddenly appeared and chases him before shooting him when the victim stumbled and fell.
Douglas Johnson, believed to be the shooter, and Austin, the getaway driver, were identified by two people who watched the programme.
At trial the jury were told that Johnson had been recruited for the job by Mr Butler’s wife and step-daughter, though neither of them were ever prosecuted in relation to the murder.
At trial the jury were told: “This case is a conspiracy theorists’ dream. It has got everything, sex, violence, blackmail, celebrity, betrayal.”
But multiple trials fell though, including one in 2008 when a judge was forced to throw out the case – at the cost of £6m to the taxpayer – as the House of Lords ruled against anonymous witnesses giving evidence.
Eventually after a third trial both Johnson and Austin were found guilty of murder.
Both were sentenced to life with a minimum term of 30 years.
Austin was a prisoner at HMP Long Lartin in Worcestershire at the time of his death.
