Businessman Andrew Bush, 48, had jetted out to his Spanish villa in April 2014 with a new lover, who found his former girlfriend Mayka Kukucova, then 26, waiting in his bed.
Bush told his new partner Maria Korotaeva, 20, to go to the car and phone the police, after the Slovakian swimwear model ex refused to leave.
But, after an argument broke out between Bush and his ex-partner, Miss Korotaeva heard three gunshots - and later found her partner in a pool of blood.
An inquest held today at Avon Coroner's Court in Bristol, ruled that Bush was murdered by Kukucova.
Kukucova was jailed in May 2016 for 15 years, but had her sentence reduced the following year to 13 years imprisonment.
Coroner Dr Peter Harrowing said that Mr Bush's inquest had been triggered by the jeweller's body finally being brought back to the UK earlier this year - five years after his death.
Dr Harrowing told the inquest that Mr Bush had been interred in a "niche" at a cemetery in Estepona, Spain, where he was killed.
"Following the fifth anniversary of his death, Andrew's sister Rachel Bush, decided to bring his body back here for a proper funeral," said Dr Harrowing.
"I am satisfied that the body returned from Spain to this jurisdiction was that of Andrew David Bush."
Dr Harrowing said that criminal proceedings had been held in Spain, where Kukucova was found guilty in a unanimous verdict in May 2016.
The coroner said: "On April 5, 2014, at 00.30, Mr Bush arrived at his house in Malaga, Spain, with his new partner. Inside the house was Mayka Kukucova.
"Mr Bush invited his ex girlfriend to leave, and when she would not, he told his current girlfriend to return to the car and call the police.
"No call was made to police at that time. Mr Bush's partner then heard an argument between Mr Bush and Miss Kukucova.
"This was interrupted when he came outside to speak with her for a few minutes.
"On his return inside the house, Miss Kukucova was waiting and unexpectedly made use of firearm, with which she shot Mr Bush up to three times, moved by a desire to end his life.
"Mr Bush did not have the possibility of reacting to defend himself.
"The first shot was to his left arm, from a distance of 1.5 metres. The other two were to his head.
"Miss Kukucova then left the scene. She was subsequently arrested and placed on trial, and found guilty of murder.
"I am satisfied beyond reasonable doubt that I can record a conclusion of unlawful killing," Dr Harrowing added.
At Kukucova's trial in 2016, the court heard how the bikini model had become "obsessed" with Mr Bush, known as the Mr Bling of Marbella, after their split in November 2013.
The 26-year-old had begun stalking him and, from April 2, 2014 - three days prior to his death - had been in his house in Malaga, Spain, without his consent.
And Russian-born Maria Korotaeva, who was seeing Mr Bush at the time of his killing, has previously told how she "cowered" in the car as he was shot three times inside the villa.
Just days after his death, the University of West of England (UWE) student, said: "There's no way of putting into words how you feel when somebody you love is killed right there in front of you.
"We had so many plans for the future and now there's nothing."
The pair had been drinking champagne in the villa, which Mr Bush had been refurbishing for her, to celebrate their anniversary.
Maria said: "When we got there it looked different. Things had been moved and there was nothing of mine. All her clothes were there.
"When I went into a room and saw her it was a shock. She was wearing pyjamas. There was so much security I could not work out how she had got in.
"When I saw her I ran out the house and locked myself in the car. I did not want a problem. I did not want any drama.
"Andy came out and said not to worry. It was all fine. He said she was a crazy bitch. That she was an illegal and he would get her out the house."
Maria was forced to walk up to the main road to find an officer because police were unable to find the villa and then fire services took two hours to find the house.
It was three hours before the firefighters broke in and found the body of Mr Bush who launched Andrew Davids jewellers, now called Gold Trader.
The couple had plans to move to London together after she had finished her degree at UWE in Bristol.
Mr Bush also left behind an ex-wife, Samantha, and daughter, Ellie Mason Bush.