The reason why a man from London took rat poison on a moor in the Pennines two days after flying back to the UK remains a mystery, an inquest has concluded.
David Lytton prompted an international hunt for clues after his identity remained unknown for 13 months, Rochdale Coroner's Court was told.
Simon Nelson, senior coroner for Greater Manchester North, recorded an open verdict in his death and said "fundamental questions remain unanswered".
Mr Lytton flew 4,000 miles from his adopted home, Pakistan, booked into a hotel for five days in London then paid for a return train ticket to Manchester.
He then went to a pub near Saddleworth Moor, asked the landlord for the way to "the top of the mountain" and wandered off into the night.
The 67-year-old had no connection to the area and was found fully clothed on a remote track near Indian's Head, the summit of Dovestone Reservoir, on 12 December 2015.
He was wearing a light mac, trousers, a shirt and slip-on shoes and was carrying £130 in cash, but had no identification and was only identified in January, despite a mass appeal in the media.
Mr Lytton had been in a relationship for more than 30 years with a woman, but did not even tell her he was moving to Pakistan in 2006 and simply left, the inquest heard.
He had not spoken to his only brother for more than 10 years and did not mention his relationship to friends.
The inquest heard from nurse Maureen Toogood, who said she was in a relationship with Mr Lytton from 1972, but added they never lived together because of his "unusual character traits".
She said he was shy, particular about his appearance, and asked her never to talk to him about his family.
Ms Toogood became pregnant, but miscarried and the relationship was never the same, she said.
In October 2006, he visited her as normal and kissed her goodbye and she never saw him again.
The inquest heard she was "flabbergasted" to find out from a neighbour that he had sold his house and emigrated to Lahore without telling her.
The inquest heard Mr Lytton, who grew up in Finchley, north London, was born David Lautenberg, but the family changed their name to Lauten, and he later changed his name again to Lytton.
His younger brother Jeremy Lauten described him as a "genius" who did well at grammar school.
He wanted to become an Oxbridge student, but failed to get the grades and eventually dropped out of Leeds University.
His brother said he became ever more "insular" and distant from his family.
He became a croupier and later a Tube driver - apparently so he could spend all day in the cab on his own without having to speak to people.
He had a house in Streatham where he lived a "minimalist" life "unencumbered with possessions", his brother said.
Mr Lauten added that his brother did not attend their father's funeral and he had not had contact with him since 2004.
But Mr Lauten was clear that he did not think his brother would not take his own life.
The senior coroner, Mr Nelson, said he was satisfied there was no third party involvement in Mr Lytton's death and that he had taken the strychnine poison "by his own hand".
"This has been an extraordinary case for obvious reasons," he said.
"Sadly, notwithstanding the quite outstanding investigative work by the police, there are many fundamental questions which remain unanswered.
"He was a complex, private individual who tended to compartmentalise his life or not reveal or share his thoughts or future plans."