The son of notorious criminal John "Goldfinger" Palmer has told for the first time how he fought to save his father's life as his family offered a £50,000 reward to catch the professional hitman who killed him.
The 65-year-old - once described as Britain's richest criminal and thought to have been worth £300 million - was found shot in the garden of his remote woodland home in South Weald, Essex, on June 24 last year.
Essex Police originally thought he died of natural causes but it later emerged he had been murdered. They now say the crime had "all the hallmarks" of a contract killing.
The case was featured on the BBC's Crimewatch programme on Thursday night and his son James Ketley described how he rushed to help his father after his girlfriend found him collapsed in the garden.
Mr Ketley added: "I heard no gunshots, it was just very, very quiet.
"I could still feel his heart beating so I thought there might be a chance we could keep him alive
"I felt so helpless because I had to watch him die in front of me."
Detective Chief Inspector Stephen Jennings said the family had independently offered the reward in the hope of catching the person or people responsible for the murder.
Speaking on the programme, his partner, Christina Ketley, said: "There may be some people out there who don't have a tremendous amount of empathy towards our situation or the loss of John but there is someone out there who is prepared to assassinate someone."
Officers said one reason for the killing may have been rumours that Palmer - who gained his nickname after being acquitted of handling gold bullion in the 1983 Brink's-Mat raid - had turned informer about his previous criminal connections and links to other organised crimes, including the £14 million Hatton Garden raid.
Detectives would not comment on whether or not he was an informer but said they were aware of speculation about this in the criminal underworld.
Palmer was due to stand trial in Spain for real estate fraud in Tenerife and it was rumoured that no further action would be taken against him, possibly reinforcing this perception.
Mr Jennings said: "We cannot comment on the truth of many of these rumours, although Mr Palmer was still due to stand trial in Spain when he was killed.
"But if people in the criminal underworld believed them then it is entirely possible that this led to someone commissioning a professional hit on him.
"Due to John's significant criminal history, there are people or groups of people who may have wished to do him harm.
"Therefore our search is not just for the gunman but for a person or group of people who may have commissioned the killing."
A man described as a "possible suspect or witness" was spotted near the house at 5.50pm on June 24 - 20 minutes after Palmer was found dead.
He is described as white, in his early 20s, about 5ft 10in and of slim build, with short blond hair and casually dressed in light blue jeans and a light coloured baggy top.
Detectives are also looking to trace two or three men seen digging a hole in the woodland surrounding Palmer's home at about 11.50am on June 23.
Detectives found a hole in the fence surrounding Palmer's sprawling grounds, which they believe the gunman used to watch his movements.
They believe the hitman climbed over the fence and struck from a short distance using a handgun in one of the only areas of the house and garden not covered by Palmer's own CCTV system.
The force released footage from this CCTV showing Palmer gardening and burning documents at about 5.18pm. That is the last time he was seen alive.
Palmer came to public attention when he was cleared of handling proceeds from the £26 million Brink's-Mat bullion raid at Heathrow.
He was jailed in 2001 for timeshare fraud, after building a multimillion-pound business which cheated thousands of Britons who wanted a holiday home in the sun.
Anyone with information about the killing is asked to contact Essex Police on 101 or Crimestoppers, anonymously, on 0800 555111.