One of the world's richest men died depressed and facing a potentially ruinous raft of court actions after a bitter multibillion-pound trial defeat to football owner Roman Abramovich, an inquest heard.

Russian oligarch Boris Berezovsky became a "broken man" and spoke of killing himself in the wake of the costly court battle with Chelsea Football Club supremo Mr Abramovich in 2012, which left him feeling as though his bank balance and his reputation had been trashed.

Friends and medical professionals spoke of the 67-year-old's frequent references to suicide, but none said they ever suspected the former Kremlin insider would kill himself.

Mr Berezovsky's lifeless body was discovered slumped on the floor by his bodyguard at his ex-wife's luxury property in Ascot, Berkshire, on March 23 last year.

Detective Inspector Mark Bissell, of Thames Valley Police, said the death was treated as "unexplained" at first.

Asked by the coroner Peter Bedford if officers had reason to believe foul play due to Mr Berezovsky's position as an outspoken Russian exile, Mr Bissell told the inquest that they took into account that he was a "high profile individual" and a "formidable and powerful businessman" with "membership within the higher echelons of the political spectrum in Russia".

He said no suicide note was found, and Mr Berezovsky had made plans for later that month.

Friends told the hearing in Windsor Guildhall that the impact of the Abramovich trial weighed heavy on Mr Berezovsky in many ways.

Bodyguard Avi Navama said his employer was "very low" and "depressed" in the last four months of his life but seemed "different" in the final two days before he died.

Speaking of when he last saw him, the night before finding him dead, Mr Navama said: "He looked at me with very low, tired eyes - like he doesn't know what to do."

The bodyguard said that, ahead of losing the court battle with Mr Abramovich, Mr Berezovsky was a "very active person, very dynamic".

But he went on: "After the verdict Mr Berezovsky was very depressed."

Mr Navama said his boss had talked frankly and openly about suicide - including once brandishing a knife.

Asked by the coroner whether Mr Berezovsky's mental health was a consequence of the fall-out from the Abramovich case, Mr Navama said: "It was the trigger of the change.

"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."

Mr Navama's wife, Zoe Watson, also described how Mr Berezovsky became "a shell of the man" she once knew.

She said that following the private litigation, which found in favour of Mr Abramovich over a £3 billion debt, Mr Berezovsky went to Israel and began taking strong anti-depressant medicine, suffering panic attacks and heart palpitations.

The alarm was raised when Mr Navama had not heard from his boss, and broke down the bathroom door suspecting the man to be inside.

Mr Navama said Mr Berezovsky's ex-wife, Galina Besharova, then arrived and became distressed when she saw the body, calling out: "Why? Why? Why?"

Mr Bissell also told the inquest that his team carried out "proportionate" inquiries into claims that the oligarch was assassinated and that his death was faked, but nothing untoward was found and suicide was concluded.

Giving evidence, paramedic John Pocock confirmed he received a phone call to say that police were warning of "hazardous materials" being present in the property and a "warning tone" went off on the alarm he carried to detect levels of background radiation.

But he said: "It may have just been a faulty meter.

"It could have been that it was an accumulation of background radiation that may have set the alarm off."

He added that there was nothing "glaringly obvious" which suggested anything other than hanging.

Mr Berezovsky's legal adviser, Michael Cotlick, told the inquest the tycoon had spoken of suicide since October 2012 but he had not taken him seriously, explaining that because he spoke of the matter to "almost everybody" he did not think he would really do it.

Mr Cotlick, who had worked for the oligarch since 2005, said he was aware he was on anti-depressants but Mr Berezovsky had told him they were having adverse effects on his liver, so he stopped taking them days before he died.

He described how Mr Berezovsky fled Russia after falling out with the Kremlin and being the subject of arrest warrants. He was granted political asylum in the UK in September 2003.

Mr Cotlick confirmed his boss was an associate of KGB spy-turned-dissident Alexander Litvinenko, who died from radioactive polonium-210 poisoning in November 2006, and he was due to give evidence at the inquest.

He said Mr Berezovsky survived a number of assassination attempts, including a car bombing which killed his chauffeur and left him seriously injured in 1994, and another that was foiled in summer 2007.

But Mr Cotlick said that losing the case against Mr Abramovich made him less of a target as the damage to his reputation reduced his power and influence.

He said another big blow to his employer was when his partner Elena Gorbunova - who had 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.

Mr Cotlick said his friend changed his will nine days before his death, but also made several plans for meetings and appointments for after March 23.

The witness played down the significance of the private litigation with the Chelsea owner.

He said: "Nobody took the outcome of the Abramovich trial seriously."

He added: "There's only one explanation - that's suicide.

"If somebody told me before that he would end his life, I would never believe it. Looking back on the past year, I think that's the only explanation."

In a written statement, former partner Elena Gorbunova said she had been in a relationship with Mr Berezovsky for 21 to 22 years but they had been going through a "commercial dispute over assets and finances" before he died, which they hoped to settle outside of the courts.

She said they spoke on the phone for 20 minutes on the night before his body was found, mainly about their daughter.

Her statement said that when she last saw him a week earlier he had not given any indication he would take his life but was aware of his depression.

The inquest also heard a written statement from Vladimir Lenski, who had a managerial role in one of Mr Berezovsky's companies.

He said the oligarch had become "very despondent" since the case with Mr Abramovich.

"He felt he had lost face with the Russian public and the government and any influence he had was greatly diminished," Mr Lenski said.

The hearing was told a wealthy Russian associate offered to help resolve Mr Berezovsky's cash flow problems, though the benefactor's identity was not revealed in court.

Psychiatrist Dr Saeed Islam said Mr Berezovsky "perceived relentless pressure on him in terms of litigation and fear of losing those cases".

He said he also spoke of "enemies in Russia who were trying to destroy him and make him homeless".

Dr Islam told the inquest that Mr Berezovsky described feeling very low and told him: "I can't see a way out."

But he said that although Mr Berezovsky had suicidal thoughts, he said it was not an option due to his Russian Orthodox beliefs and his family.

Facing questions today from Mr Berezovsky's family about their loved one's mental state, Dr Islam said: "Somebody who wants to do it (suicide) will do it."

The hearing, which is expected to last for two days, was adjourned until tomorrow morning.