An inquest into the death of a man whose body was found in mysterious circumstances on Saddleworth Moor has recorded an open conclusion.
David Lytton, 67, from London, was discovered at Dove Stone Reservoir in Greater Manchester on 12 December 2015.
It took police more than a year to establish his identity, and a pathologist said the most likely cause of death was strychnine poisoning.
Coroner Simon Nelson said he could not be sure of Mr Lytton's "intention".
"Whilst accepting he died of his own hand, the only appropriate conclusion I can reach is an open conclusion," he said.
Police ruled out any suspicious circumstances, but Mr Nelson said a series of "fundamental questions remain unanswered".
Find out more
"He was a highly complex, private individual who tended to compartmentalise his life or not reveal or share his thoughts or future plans."
The death sparked worldwide interest as a police investigation was launched to identify the body of the man, first nicknamed Neil Dovestones by mortuary workers at Royal Oldham Hospital.
It was discovered Mr Lytton had lived in Pakistan for 10 years and had flown to London Heathrow two days before his body was found, the inquest at Rochdale Coroner's Court was told.
It emerged he had paid cash for a five-night hotel stay in the capital, but travelled north after one night despite having no known links to the area.
When found, he had no wallet, phone or documents but a breakthrough came when a post-mortem examination found a metal plate in his leg which had been fitted in an operation in Pakistan.
Officers later matched an artist's impression with a passport photo in a list of passengers on a flight to the UK.
The National Crime Agency was then able to determine that Mr Lytton had lived in Lahore.
Police traced his next of kin and his identity was eventually confirmed following a DNA match with his mother.
It later emerged he had changed his name in 1986 from his birth name, David Lautenberg.
Strychnine is most commonly used as mole poison, the inquest was told, and there were traces of the substance in a medicine bottle found with Mr Lytton's body.
Mr Lytton's brother, Jeremy, described him as a "genius" who did well at grammar school and wanted to become an Oxbridge student.
But he failed to get the grades and eventually dropped out of a sociology and psychology degree at Leeds University and became ever more "insular" and distant from his family.
He became a croupier and later a driver on the London Underground, so he could spend all day in the cab on his own without speaking to people.
Mr Lytton had been in a relationship for more than 30 years with a woman, but did not tell her he was moving to Pakistan in 2006 and simply left, the inquest heard.
Det Sgt John Coleman of Greater Manchester Police described the case as "unlike anything I have ever known" in 20 years as a police officer".
The mystery gave rise to a number of theories about Mr Lytton's death, which were later discounted.
There was speculation he could have been making a final journey to the site of a plane crash in 1949, while a man from Northern Ireland contacted police to say he could be missing Hugh Toner, from Newry, who disappeared in 1994.