Russian tycoon and ex-politician Boris Berezovsky told the High Court that Roman Abramovich, the owner of Chelsea Football Club, had been "like my son" and that he was a "genius".
Mr Berezovsky was cross-examined by Mr Abramovich's barrister, Jonathan Sumption QC. He is suing Mr Abramovich for more than £3bn, which he claims the latter owes him after forcing him to sell his stake in Sibneft, a hugely profitable oil firm.
Mr Abramovich "is genius", he said. "If he wants to convince somebody personally, he may serve them so well. And you trust him so much that you really believe he is sincere. He is genius. He really convinced me for a long time he is like my son."
Mr Berezovsky is expected to give evidence for most of next week. Yesterday he appeared far more comfortable than on Thursday, when he had often struggled to answer questions, and denied claims that were later shown to be in his witness statement.
Mr Berezovsky, 65, is claiming for alleged breach of trust and breach of contract, after he and Mr Abramovich fell out in 2000, having previously, he claims, been very close friends.
Mr Berezovsky claims that Mr Abramovich forced him to sell shares in Sibneft for $1.3bn (£836m), which he contends was far below their market worth. The High Court case is the latest installment of a long-running legal saga over the matter.
He says Mr Abramovich told him that if he did not sell the shares, then Russian President Vladimir Putin would expropriate them and he would receive nothing.
Mr Abramovich says Mr Berezovsky did not hold a profit-sharing stake in the company, and the payment acknowledged his "debt of honour" to his former mentor, without whose political influence in Boris Yeltsin's Kremlin, he would have been unable to set up Sibneft.
The case is expected to last up to three months, and is said to be costing up to £50 a second in legal fees. Mr Sumption is reported to be receiving a £10m fee. Mr Abramovich is due to give his evidence in November.Reuse content