A court will rule on whether Roman Abramovich has won a £3 billion legal fight with Boris Berezovsky on Friday, the Judicial Office has said.
Berezovsky claimed Abramovich had "intimidated" him into selling shares in the Russian Sibneft oil company for a fraction of their value and had also broken a promise made in an aluminium company deal.
The 66-year-old alleged blackmail, breach of trust and breach of contract, making his claims during a High Court case that began in October 2011 and ended this January.
Abramovich denied the allegations, and also denied that Berezovsky was entitled to damages.
Judicial Office officials said High Court judge Mrs Justice Gloster would deliver her ruling and give a summary of her judgment in London.
Laurence Rabinowitz QC, representing Berezovsky, told the trial Berezovsky and Abramovich had worked to acquire Sibneft following the collapse of the Soviet Union two decades ago, becoming friends.
Rabinowitz told the trial that Berezovsky alleged Abramovich later "intimidated" him and a colleague into selling their ownership share in Sibneft at a "massive undervalue", leaving Berezovsky "in fear for the life of his friend".
Jonathan Sumption QC, representing Abramovich, told the trial that Berezovsky had been paid millions of pounds by Abramovich businesses for his role a "political godfather".
But he said he had neither contributed "a single cent" to acquiring or building up Sibneft, nor made a managerial contribution.
Rabinowitz said that, in 2003, the Chelsea owner had agreed to hold half a 50% stake in aluminium giant RusAl on trust for Berezovsky and a colleague - but had then sold half the stake to another Russian oligarch. Sumption said Abramovich disputed that claim.
The lawyer said events had been played out against a background of "no rule of law" in Russia at that time, with police "corrupt" and courts vulnerable to "manipulation".
He said it was tough for UK lawyers to evaluate the behaviour of those who had lived and operated in such an environment.
The two oligarchs gave evidence in person. Rabinowitz said Abramovich had put on a "performance" that was a "cynical and deceitful manipulation of the trial process", while Sumption told the judge Berezovsky had been "persistently and deliberately untruthful".