A 50-year-old man has been questioned on suspicion of the murder of notorious Solihull gangster John “Goldfinger” Palmer.
The 65-year-old was found dead in the garden of his gated home in Brentwood, Essex in June 2015.
Police said they had questioned a man originally from Tyneside but currently living in southern Spain.
Although Essex Police originally thought he died of natural causes, it emerged he had been shot six times.
An inquest held in Chelmsford on December 20, heard that two police officers went to the house on June 24, and initially the death was treated as non-suspicious.
A post-mortem examination was started on Mr Palmer’s body on June 29 but was stopped when additional injuries were identified and it appeared the cause of death could be suspicious.
The examination later established he had been shot six times with a weapon believed to be a handgun.
Extensive enquiries have been conducted by detectives in to Mr Palmer’s murder, and public appeals have been made including on BBC Crimewatch.
Palmer was once described as Britain’s richest criminal and was thought to have been worth £300 million.
He came to public attention when he was cleared of handling proceeds from the £26 million Brink’s-Mat bullion raid at Heathrow in 1983, but was jailed in 2001 for timeshare fraud.
He is also believed to have links to the Hatton Garden heist and was believed to be under investigation for another fraud offence at the time of his death.
Detective Chief Inspector Stephen Jennings of the Kent and Essex Serious Crime Directorate said: “I am satisfied that Mr Palmer’s murder bares all the hallmarks of a professional contract killing involving organised crime.
“Extensive public appeals have yet to provide information which has been able to assist my team in bringing any charges against the person or people responsible for Mr Palmer’s death.
“It has been widely reported that Mr Palmer had been involved in crime both in the UK and Europe and I continue to examine the links between his lifestyle and the manner in which he was killed.
“I am still appealing for a man which was seen in Weald Country Park at 5.50pm on the day Mr Palmer was shot to contact me.
“The park is next to Mr Palmer’s home.
“The man was white, aged in his early 20s, around 5ft 10ins tall and of slim build.
“He had short dark blond hair and wore light blue jeans and a light coloured baggy sweat top.
“I would like this man or anyone else who has information about Mr Palmer’s death to contact me or my team.”
Anyone with information should contact Brentwood Major Investigation Team on 101 or Crimestoppers anonymously on 0800 555 111.
