While outside he "stumbled" and fell to the pavement. Mr Shand spent nine hours in a coma but doctors could not save him.
Over the course of the night he downed a total of five whiskies, according to a witness. At an inquest today, a coroner said "sadly" alcohol played a major role in his death.
He added that it was "significant" that Mr Shand's skull was unusually thin in parts, explaining that someone with a normal skull might have survived the fall.
The charity event, which was attended by Princess Eugenie, raised almost £1million (NZ$2 million), and was followed by an after-party at the exclusive Diamond Horseshoe club, off Times Square.
Alexandra Bowes-Lyon, a 29-year-old socialite who works for the trust, told the inquest that she spent the night by Mr Shand's side and said he had been "happy and jovial".
Drinks and dancing before fall
Miss Bowes-Lyon, who flew over to the UK from her home in New York for the inquest, said: "Mark and his team had been working very hard on very little sleep in the days before the auction.
"We had been full-on - very little sleep and a lot of work. Mark came into the office around 10am on the morning of the auction and seemed very well and jovial.
"Pre-auction cocktails started at 6.30pm. Mark maybe had half a glass of champagne to drink but he didn't have much because he was nervous about the auction.
"The auction was finished by about 8.30pm or 9pm. Mark was extremely happy with the results.
"Around 9.30pm to 10pm we went to JG Melon for burgers. By dinner Mark had had two to three whiskies. At dinner he had a whisky, we had a tequila.
"Afterwards we all got in taxis and went to the Diamond Horseshoe nightclub which was where the after-party was that we had organised for the artists.
"We danced a bit but not for long before we sat down again. We were among the last guests to leave.
"We then went to the Rose Bar at the Gramercy Park Hotel. Mark drank a whisky. At one point Mark's favourite Rolling Stones track came on and we got up to dance.
"We were only there for about half an hour. Mark suggested we went outside for a cigarette. We were standing outside just talking. I don't smoke but Mark was having a cigarette.
"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."
An unusually thin skull
A post-mortem examination revealed Mr Shand had suffered a large fracture to his skull and a bleed on the brain as a result of the fall.
Mark Deverell, a pathologist, said Mr Shand's skull was unusually less than one millimetre thick in places.
His conclusion was Mr Shand, from the village of Stourpaine in Dorset, died as a result of intra-cranial haemorrhage with a skull fracture and blunt trauma.
The inquest in Bournemouth heard that because Mr Shand's body had been embalmed it was "unsuitable" to carry out a toxicology report.
However, a blood sample taken at the Bellveue Hospital Centre in New York, where Mr Shand was taken, showed there was 210 milligrams in 100 millilitres of blood - more than twice the UK drink drive limit.
Mr Sheriff Payne, the Dorset coroner, recorded a verdict of accidental death.
Mr Payne said: "The post mortem showed there were no signs of a heart attack so sadly alcohol plays a prominent part of 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."
Mr Shand was the younger brother of Camilla and sister Annabel Elliot. He had a daughter Ayesha, 20, from his marriage to Clio Goldsmith.
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 was known for his conservation work, most notably with Asian elephants.
He set up charity Elephant Family in 2002 to protect endangered Asian elephants from extinction.
Mr Shand's 2012 book Travels on My Elephant documented his 966km journey across Indian with his elephant Tara.
- Daily Mail
