The family of murdered criminal John 'Goldfinger' Palmer is offering a £100,000 reward to help find a killer who gunned him down in his back garden in Essex three years ago.
His partner has said she is haunted that he was "stalked like an animal" by a suspected hitman who is believed to have scratched a spyhole in his garden fence before shooting him six times.
Palmer - once described as Britain's richest criminal and thought to have been worth £300 million - was found dead in the garden of his remote woodland home in South Weald, Essex, on 24 June 2015.
His family has put up a £100,000 reward, with the support of Crimestoppers, for information leading to the arrest and conviction of his killer or killers.
Detective Chief Inspector Stephen Jennings said there is "no reason for us to believe that the money put up by members of John's family is the proceeds of criminality".
Click to watch a report by ITV News Anglia's Hannah Pettifer
Essex Police have released crime scene photos of the hole in the 5ft (1.5m)tall fence panel, believed to have been scratched with a nail or another sharp object, and of a bullet recovered from the scene.
Officers originally thought Palmer had died of natural causes because of recent keyhole surgery to his chest, but it later emerged he had been shot six times at close range.
An inquest in 2016 heard there were "failings on behalf of Essex Police" andconcluded Palmer was unlawfully killed.
Christina Ketley, Mr Palmer's partner, said: "It haunts us every day to thinkthat whoever was responsible was clearly watching John, stalking him like an animal before so brutally and callously ending his life.
"Losing a loved one is hard enough but in this case we have the added stress of not only not knowing who did it but why."<
Mr Jennings said he believed it was a "professional contract killing" whichhappened in the only part of the garden not covered by CCTV.
He said he believed the killer watched Palmer until he went to make a bonfire to burn some old documents, and then jumped over the fence.
A ballistics expert concluded that the gun used was a .32 calibre silencedrevolver, which has never been found, Mr Jennings said.
Palmer was shot in the right elbow, right breast, right upper abdomen, top ofthe back, left renal area and left bicep.
Mr Jennings said Palmer, who gained his nickname after being acquitted ofhandling gold bullion in the £26 million Brink's-Mat raid in 1983, hadassociated with some of the people convicted over the £14 million Hatton Garden raid in 2015 and had been due to stand trial in Spain over alleged real estate fraud.<
Detectives are continuing to appeal for information about a man and woman seen near Palmer's home the day before the murder.
A man was also seen in Weald Country Park, next to Palmer's home, at 5.50pm on the day he was shot.
He was white, in his early 20s, around 5ft 10in and of slim build, with shortdark blond hair.
He was wearing light blue jeans and a light-coloured baggy sweat top.
Anyone who believes they have information about the murder of Palmer is asked to call Essex Police on 101 or Crimestoppers anonymously on 0800 555 111.