The Duchess of Cornwall’s brother died after a night of champagne, whisky and dance, an inquest heard on Tuesday.
Mark Shand, 62, stumbled and smashed his head outside a New York luxury hotel. He went into a coma and died nine hours later.
The coroner said alcohol played a major role in the tragedy last April.
Mr Shand had suffered major bleeding on the brain, according to a post-mortem examination.
A contributing factor was that his skull was unusually thin – just one millimetre in places – and had fractured.
Just hours before he died Mr Shand was hosting an auction for his endangered species charity, The Elephant Trust. Attended by Princess Eugenie, the Sotheby’s event raised nearly £1million and was followed by dinner and then a party at the exclusive Diamond Horseshoe club off Times Square.
Mr Shand’s group then went to the Rose Bar at the Gramercy Park Hotel, according to his colleague Alexandra Bowes-Lyon.
“At one point Mark’s favourite Rolling Stones track came on and we got up to dance,” the 29-year-old socialite told the inquest.
“We were only there for about half an hour. Mark suggested we went outside for a cigarette.
“We were standing outside just talking. He stumbled back and fell straight back. He took one step but then he fell straight down rather than stumbled.
“He had seemed just like normal Mark up until then – it was very sudden.”
By this point Mr Shand had downed five whiskies and a glass of champagne. The Rolling Stones tune is thought to have been Satisfaction.
Mark Deverell, the pathologist who examined his body, concluded that Mr Shand died as a result of intra-cranial haemorrhage with a skull fracture and blunt trauma.
The inquest heard that because Mr Shand’s body had been embalmed it was “unsuitable” for scientists to carry out a toxicology report.
However a blood sample taken from Mr Shand at the Bellevue Hospital Centre in New York showed he had 210 milligrams of alcohol in 100 millilitres of blood – more than twice the UK drink drive limit.
Sheriff Payne, the Dorset coroner, recorded a verdict of accidental death at the hearing in Bournemouth.
Mr Payne said: “The post-mortem examination showed there were no signs of a heart attack so sadly alcohol plays a prominent part in the outcome.
“It is also significant that he had a very thin skull in parts. What someone else with a normal skull might have survived he did not in this case.
“I therefore record a verdict that Mark Roland Shand’s death was an accident.
“It was an entirely unexpected event at the end of what was a very successful and enjoyable evening for his charity.”
Miss Bowes-Lyon, who flew over from her home in New York for the inquest, said she was at Mr Shand’s side all day and he had been very happy with the results of the auction. Mr Shand, who lived in the Dorset village of Stourpaine, was the younger brother of Camilla Parker Bowles and their sister Annabel Elliot.
Annabel’s husband Simon, a Dorset landowner and son of Air Chief Marshal Sir William Elliot and Rosemary Chancellor, was also at the inquest.
Mr Shand had not written a will and his estate, worth close to £1million, went to his 20-year-old daughter Ayesha who is an art student in Italy. He attended Milton Abbey school in Dorset until the age of 16 when he was expelling for smoking cannabis. He then worked as a porter for Sotheby’s before setting up a business selling Cartier jewellery.
In 1988, Mr Shand travelled to India where he found his love of elephants. He gave up his job selling jewellery in 2002 and founded his charity that protects Asian elephants.
His 1992 book, Travels on my Elephant, documented a 600-mile journey across India.
Daily Mail