Just 17 days after becoming the first Greek to climb Everest, Mr Niarchos took a fatal cocaine overdose at his flat in Mayfair, central London. The 37-year-old godson of the former King of Greece was so desperate for the drug that he dried out wet cocaine in the microwave and ate lumps the size of 50 pence pieces, Westminster Coroner's Court heard yesterday.
Medical experts told the court that Mr Niarchos had consumed 25 times the normal level of cocaine found in deaths relating to the drug, an amount which has only been exceeded by a smuggler who brought the drug into Britain in his stomach.
Michelle Lutken de Massy, a former lover of Mr Niarchos and friend of 20 years, was with him on the night of his collapse. She did not attend yesterday's inquest, but in a statement explained how he had indulged in his fateful cocaine binge.
In recent years friends and family had assumed that Mr Niarchos had kicked his drug habit after channelling his thrill-seeking instinct into fitness fanaticism. Ms Lutken de Massy's account of the events of the night of 31 May show just how wrong they were.
She described how he telephoned her and asked her to come to his flat in Grosvenor Square. She arrived at about 8.30pm to find him shaking and tense. They hugged, talked about old times and looked at the photographs of his trip to Everest.
"Constantine had a bag of cocaine in his hand," Ms Luken de Massy said in her statement. "It looked like about an ounce. He was complaining it was wet and that he could not snort it like that. He put some in the microwave. He became impatient and started to eat it.
"He took it out from the microwave and chopped it with his credit card on the worktop into lines. I had two lines. I saw him snort at least four. After this, Constantine reached into the plastic bag with the rest of it inside. He pulled out a handful about the size of a 50p piece, put it in his mouth and ate it.
"It looked to me like more than one gram. He tried to put some in my mouth too but I spat it out. I then left to go upstairs because of the sort of mood he was in.
"I could not sleep because of the cocaine and I then went to look for him. The bathroom light was on. I saw him lying on the floor. I shouted at him and he gargled in his throat."
Ms Lutken de Massy called an ambulance at around 7am. Mr Niarchos was taken to St Mary's Hospital in Paddington, west London, but was pronounced dead just before 8am.
The coroner, Dr Paul Knapman, yesterday recorded a verdict of death by non-dependent abuse on Mr Niarchos. "In recent times, he had done a lot of mountain climbing, and had climbed Mount Everest," said Dr Knapman. "The amount of cocaine (in his blood) was at a very high level. An amount exceeding this has only been found in somebody who had swallowed it in the course of an attempt to smuggle cocaine in packets into this country.
'This is a very high level indeed of cocaine. The cause of death was cocaine intoxication. This is only another example, as if one were needed, of the danger to life from taking cocaine.'
Mr Niarchos, known as "Gus", was one of the world's richest men. He inherited a share of an estimated pounds 7bn fortune after the death of his father, Stavros, in 1996. He was based in the Swiss ski resort of St Moritz. His first marriage to Princess Alessandra Borghese ended in divorce after a year.
He had a history of narcotics abuse, starting with an expulsion from Harrow school for possessing drugs.
He then went to Gordonstoun - and left in similar circumstances. He was a contemporary of Prince Andrew and Prince Edward at Gordonstoun and was expelled after one of the princes' detectives found cannabis in a hollowed- out chair leg.
In 1997 he checked into the Betty Ford Clinic in California for treatment for alcoholism and drug abuse. In the same year he married a Brazilian artist, Sylvia Martins, with whom he had had a five year relationship.
He took up sport, which many saw as his salvation. He reached the summit of achievement in conquering Everest, but did not, it seems, survive the celebration.