A coroner recorded an open verdict into the death of Russian oligarch Boris Berezovsky today.
After summing up the two days of "contradictory" evidence, Berkshire coroner Peter Bedford said he could not prove beyond all reasonable doubt that the businessman either took his own life or was unlawfully killed.
The body of the former Kremlin insider was discovered slumped on the bathroom floor at his ex-wife's luxury property in Ascot, Berkshire, with a ligature wound to his neck on March 23 last year.
Mr Bedford told the inquest at Windsor Guildhall: "I am not saying Mr Berezovsky took his own life, I am not saying Mr Berezovsky was unlawfully killed.
"What I am saying is that the burden of proof sets such a high standard it is impossible for me to say."
Members of the Berezovsky family declined to comment on the verdict as they left the court.
The inquest heard Mr Berezovsky had often spoken of suicide and became a "broken man" after losing a multibillion-pound court battle with football club owner Roman Abramovich in 2012.
The former Kremlin insider, who fled Russia after falling out with the government, fell into a deep depression as he faced financial ruin and the loss of his reputation after the judge found in favour of Mr Abramovich over a £3 billion debt.
The coroner said: "It is clear to me and the witnesses I have heard that it had a significant effect not only on his finances but also on his mental health."
Although there were suggestions that the 67-year-old - who had survived at least two assassination attempts - was murdered, police did not find any evidence of foul play.
Forensics experts also said they concluded he died at his own hands but a professor called in by the family to give evidence this afternoon suggested the marks around his neck indicated he had been strangled and then made to look like he had hanged himself.
Police confirmed that they carried out "proportionate" inquiries into claims that the "formidable and powerful" businessman was assassinated or had even faked his death.
Detective inspector Mark Bissell, of Thames Valley Police, told the inquest officers took into account the fact that he had "membership within the higher echelons of the political spectrum in Russia" but no evidence of any third party involvement was found, although an unidentified fingerprint found in the bathroom remained unaccounted for.
Dr Simon Poole, the Home Office pathologist who carried out the post-mortem examination on Mr Berezovsky, said no defence wounds indicating a struggle were found, adding: "These injuries were extensively looked for."
He said he concluded the cause of death was hanging consistent with self application of the ligature and there was no evidence of any other involvement.
But Professor Bernd Brinkmann, an expert on hanging and asphyxiation cases, told the hearing that he believed two people were involved in his death.
Prof Brinkmann said: "In my view there is no way for death by hanging. There exists two major, major concerns against."
Prof Brinkmann, who said his family was friends with the Berezovskys, said the marks on his neck were "far away from the typical inverse 'V' shape" usually seen.
He also said that "congestion" to Mr Berezovsky's face was not consistent with being hanged.
He suggested the exiled Russian could have been attacked suddenly from behind and quickly strangled, which was why there were no signs of a struggle.
He said he thought that Mr Berezovsky, who he said weighed 80kg, could have been attacked in his bedroom and his body then moved into the bathroom where he was found.
Referring to his evidence during his summing up, the coroner pointed out he had only based this on photographs of the body, which "put him at a disadvantage of giving a complete and full analysis of all of the issues".
The coroner added that there did not appear to be any motive for killing Mr Berezovsky, noting evidence from his legal adviser Michael Cotlick that his loss of reputation and influence as a result of the Abramovich case meant his enemies now preferred him alive to use as a scapegoat.
Giving evidence earlier today, his daughter Elizaveta Berezovsky said she thought her father had been poisoned when he spoke of feeling a chemical imbalance, which was later put down to his depression.
She told the hearing: "He was a target, always. My father was a very serious political figure."
She said that if he had recovered from his illness he might have appealed against the Abramovich case and recovered his former standing.
She also criticised the health professionals who treated him, suggesting they could have done more to prevent his death.
The inquest heard that although they knew he was ill, his family found it hard to accept he would have killed himself.
Witnesses described how he went from being a dynamic, active person to a "shell" of a man who often spoke of suicide - even asking them for advice on how to go about it.
His rapid loss of fortune meant he was forced to move out of his own mansion and become a guest at the home of his ex-wife Elena Gorbunova while he could not afford to keep on most of his staff.
Another big blow to him in the months before his death was when his partner, Elena Gorbunova, who sat at his side throughout much of his battle with Mr Abramovich, filed a financial claim against him which had the potential to financially ruin him.
The inquest heard that Mr Berezovsky, who did not leave a suicide note, had also recently been troubled over issues regarding his youngest daughter's schooling.
His bodyguard of six years, Avi Navama, was the last person to see him alive on the evening of March 22 and found his body the next day.
Speaking of when he last saw him Mr Navama told the inquest: "He looked at me with very low, tired eyes - like he doesn't know what to do."
He added: "After the verdict Mr Berezovsky was very depressed. He told me he was in minus £200 million that he can't pay to people.
"He would say he's not a billionaire, he's the poorest man in the world."
The inquest heard Mr Berezovsky had been taking strong anti-depressants and suffered panic attacks and heart palpitations. But he stopped taking the medication just a few days before his death after being told by his doctor they were having an adverse effect on his liver.
The coroner said that although some witnesses believed his death was suicide, others had said Mr Berezovsky's mood "fluctuated" and he appeared to be happier just before his death.
The inquest heard he was making plans for the future and was due to travel to Israel.
Mr Bedford said: "It's perfectly possible in my view that he could have presented himself to one person as well and optimistic and would within a matter of a short period present himself as low and heavily depressed."
Thames Valley Police later issued a statement saying they and the South East Counter Terrorism Unit had carried out a thorough investigation into the death.
"This included the deployment of an experienced Home Office pathologist to examine the body in situ and conduct the subsequent post mortem.
"His findings were considered alongside examination of the ligature, detailed toxicology, physical evidence recovered from the scene and the deceased's medical history.
"The investigation could find nothing to support the hypothesis of third party involvement.
"In reaching his verdict the coroner Mr Bedford made it clear he had no criticism of the police investigation. He stated that his open verdict was as a consequence of conflicting expert testimony regarding pathology.
"It is proper for the investigation to consider the alternative pathology position. This position was only brought to police attention immediately before the inquest.
"We would stress that the coroner has not specifically requested that any additional work take place. We will continue to liaise with family members as we have done throughout this process."