Detectives believe they know who killed gangster John 'Goldfinger' Palmer and why... but the

WHODUNNIT? Intelligence has provided names to Essex Police but they still can't make arrests (PA)

DETECTIVES probing the murder of gangster John Palmer believe they may know who killed him but do not yet have enough evidence to make arrests.

DS Stephen Jennings, who is leading the investigation for Essex Police, said the case now focussed on a few key suspects, but there is not yet enough evidence to arrest them.

The National Crime Agency (NCA) has been drafted in to help with the investigation due to the scale of Palmer's top level criminal associates.

Essex Police is also investigating if Palmer could have been a victim of the notorious Hatton Garden burglary.

THEORY: It has been suggested Palmer had a box containing incriminating evidence (PA)

They are investigating if he had a safety deposit box holding compromising material about rival crime lords at the Hatton Garden Safe Deposit Company.

One theory is that the Brinks Mat crook, who was known to record all his meetings, had incriminating evidence about unsolved gangland murders stored in the vault that was famously burgled in April 2015.

Mr Jennings said it was still "an active line of inquiry" when asked if the force had ruled out the kingpin having a safe deposit box there, that could have led to his killing after its contents were retrieved.

EVIDENCE: A bullet casing retrieved from the scene (Essex Police)

Palmer, 65, was shot six times in his garden in Brentwood, Essex, in June 2015, just weeks after the first arrests in connection with the multi-million pound burglary.

Mr Jennings said there was no evidence to suggest Palmer, once worth an estimated £300 million, had been involved in arranging the burglary.

However, enquiries had shown he was a known associate of some of those convicted.

Yet, Mr Jennings believes the murder probably happened as a result of a major fraud trial in Spain that Palmer and ten of his associates were charged in connection with in May 2015, also just a few weeks before his death.

It is thought members of the underworld killed him because it was feared he was about to turn informant in a deal with Spanish prosecutors.

JAILED: Palmer's former righthand man Richard Cashman (Poker Red)

Last week Palmer's henchman Richard Anthony Cashman, 52, originally from the north east, was jailed in Madrid for running Palmer's multi-million pound Tenerife timeshare scam while the kingpin was serving a prison sentence in HMP Long Lartin after being convicted over the same scam in the early 2000s.

Darren Morris, a nephew of Palmer, got 30 months for fraud and illegal possession of a 9mm Zastava pistol believed to have been Palmer's, while four others were jailed for fraud.

Mr Jennings said: "Speculation was rife in the underworld and media both in the UK and abroad, that Mr Palmer may have been seeking a deal with Spanish prosecutors in order to have the charges dropped. There is nothing to suggest this was true."

CHARGED: Christina Ketley in court left of Cashman (far right) (Timeshare.net)

He said prosecutors had been interviewed and there was no evidence of any contact between them and Palmer concerning such a proposed deal.

He said: "My view is that someone involved in that trial may have still felt it was not in their interest for him to be there to represent himself."

Cashman returned to the UK to attend a voluntary interview in February 2017, but was never arrested.

Also of interest to the investigation is the ongoing extradition to Spain of Paul Blanchard, 73, from York.

ACCUSED: Paul Blanchard faces extradition to Spain (The Cheavours)

He is accused of money laundering in his role as finance advisor to Mohamed Jamil Derbah, 55, a one-time partner of Palmer's who became embroiled in a feud with him after setting up a rival timeshare operation on Tenerife.

Blanchard is fighting the extradition amid claims he only worked with Derbah for the Spanish security services to get information for them.

Mr Derbah also released last year a book about his feud with Palmer.

Mr Jennings said: "I am certainly aware of this extradition process and am aware of Mr Derbah and his association with John Palmer. I have obtained the book Mr Derbah wrote."

ASSOCIATE: Mohamed Jamil Derbah worked with then feuded with Palmer (Mohamed Derbah)

Yesterday, police renewed their appeal and stressed a £100,000 reward for information remains available.

Since the last appeal in June more statements have been taken from potential witnesses and documents obtained, but no further arrests made.

He said: "We did get a few lines on enquiry that we are still looking at

"We are working closely with the NCA who have been extremely helpful."

He said intelligence had narrowed down a small number of suspects, but more evidence was needed to make arrests.

PROBE: DS Stephen Jennings can't yet prove who killed John Palmer (Essex Police)

Mr Jennings hopes the Spanish trial and two trials linked to Hatton Garden all concluding this year will make underworld figures more willing to speak out.

He said: "In the last year there have been significant developments and events within the criminal underworld that may now mean people who have information may feel able to come forward.

“The fraud trial in Spain has now concluded. There is always nervousness within the underworld when a trial is looming. Now that it has concluded people may feel they can talk to us."