Chelsea Football Club owner Roman Abramovich operated in a Russian state which had "no rule of law" following the collapse of communism nearly two decades ago, the High Court was told today.
A barrister representing the billionaire Russian businessman said "quite extraordinary conditions" existed in a country where police were "corrupt" and courts open to "manipulation".
Jonathan Sumption QC told Mrs Justice Gloster it was "not easy" for English lawyers to assess the behaviour of people who lived in "such a world".
He was speaking while summarising Mr Abramovich's defence in a multi-billion pound legal battle at the Commercial Court in London.
Mr Abramovich is being sued for more than £3 billion by fellow Russian oligarch Boris Berezovsky, in a case which began this week and is expected to last for more than two months.
Mr Berezovsky is claiming Mr Abramovich "intimidated" him into selling shares in Russian oil company Sibneft at a fraction of their value - and alleging breach of trust and breach of contract.
Mr Abramovich denies the allegations, disputes that "oral agreements" were made and denies that Mr Berezovsky is entitled to damages.
Both men were at today's hearing.
Mr Sumption said Mr Berezovsky was paid millions of pounds by businesses controlled by Mr Abramovich for his services as a "political godfather".
By the late 1990s Mr Berezovsky's personal expenses were met by Mr Abramovich's companies, said Mr Sumption.
They were on an "exuberant scale" - funding "palaces in France", "private aircraft", "jewellery for his girlfriend" and "valuable paintings But he said Mr Berezovsky's contribution had been "almost entirely political".
He said Mr Berezovsky, who controlled a "powerful media empire", in Russia had a "close relationship" with people in the "immediate circle" of then President Yeltsin.
"Mr Berezovsky persuaded the Russian Government to sell the right to manage Sibneft on the state's behalf under an auction procedure which was easy to rig and was, in fact, mainly rigged by Mr Berezovsky himself," said Mr Sumption.
"His contribution was important, indeed it was indispensable. But it was almost entirely political."
Mr Sumption said that, without Mr Berezovsky's "considerable influence", Mr Abramovich "would have got nowhere".
"(Mr Abramovich) always recognised that he would have to pay Mr Berezovsky," added Mr Sumption. "He owed Mr Berezovsky a great deal."
But Mr Sumption said Mr Berezovsky had not "contributed a single cent" to acquiring or building up Sibneft, nor made any managerial contribution.
The hearing continues tomorrow.