Chelsea Football Club owner Roman Abramovich will find out on Friday whether he owes his former partner Boris Berezovsky as much as $6 billion after a British court battle that has laid bare the post-Soviet carve-up of Russia's vast natural resources.

After a legal odyssey stretching from the gilded corridors of the Kremlin to the offshore enclaves favored by Russia's richest tycoons, Judge Elizabeth Gloster will rule on whether Berezovsky was extorted out his business empire by Abramovich.

Berezovsky, a fast-talking former mathematician who became a Kremlin powerbroker under late President Boris Yeltsin only to fall foul of Vladimir Putin, says Abramovich used the threat of Kremlin retribution to intimidate him into selling out of Russia's fourth biggest oil company at a knockdown price.

Abramovich, the world's 68th richest man with a $12.1 billion fortune, denies that and says he merely paid Berezovsky money for political cover and protection - known in Russian bandit slang as "krysha" or "roof".

"I am a genetic optimist but I shall not say anything more until we see the verdict," Berezovsky told Reuters by telephone on Tuesday.

Judge Gloster will spend about an hour reading out a summary of the decision at the High Court's modern Rolls Building, starting at 09:30 GMT on Friday. The final judgment will be published after September 17.

Abramovich spokesman John Mann declined to comment until the ruling was handed down, though either party could appeal in the case, which has cost tens of millions of pounds in legal fees.

Besides the personal drama of a public battle between two of Russia's most dazzling businessmen, one of the biggest private litigation cases in the world has detailed the treacherous business world of post-Soviet Russia:

Ownership means nothing, offshore cash is king and while Yeltsin granted favored tycoons control over the oil and metals producers of a former superpower, President Putin can wrestle assets back from errant oligarchs no matter how powerful.

Russian Krysha

Complete with blatant tax evasion, informal deals on billion-dollar assets and a fly-on-the-wall view from inside the adrenaline bubble of Russia's A-team of oligarchs, the case reveals the country's heady corruption.

Even the evidence reads like a John le Carre thriller: barristers bickered over handwritten notes from an offshore lawyer who died in a mysterious helicopter crash, a snatched conversation on tax avoidance recorded in secret at Le Bourget airport and a meeting at London's Dorchester Hotel to hash out the creation of the world's biggest aluminum company.

"The most interesting part of it is the light it sheds on the way in which Russian business was done at that very high level in the immediate post-Communist period: This culture of krysha and payments being paid back and forward," said Philippa Charles, a litigation partner at law firm Mayer Brown, which is not directly involved in the case.

"Meetings at heliports, alpine ski resorts - it is all rather James Bond but actually it shows this was the reality of how business was done at that time in Russia," Charles said.

The focus of the case was 1995 - the year Yeltsin sold off the assets of a former superpower to a handful of influential traders who became known as the oligarchs.

Rich beyond the dreams of their often modest Soviet childhoods, the barons of Siberia came to personify the corruption of post-Soviet Russia: brash, dangerous alpha-males who scorned the rules of mortals.

After meeting on a Caribbean yacht trip organized by fellow tycoon Pyotr Aven, Berezovsky and Abramovich, then a 28-year-old oil trader, came up with a simple idea: merge Russia's best refinery with some of the top oil and gas fields of Siberia.

But to pull it off, they would need Yeltsin's support.

Oligrach battles

Berezovsky said Abramovich agreed to give him and partner Badri Patarkatsishvili, a chain-smoking Georgian who died in Britain in 2008, a half share of what would become Sibneft to secure state approval for its creation and privatization.

Abramovich disputes that, saying he merely paid Berezovsky for providing political cover and protection culminating in a final payment of $1.3 billion via a sheikh in 2001. Abramovich said Berezovsky did nothing to develop Sibneft.

"Krysha was required. It was impossible to keep hold of the company without krysha. So we required both political and physical krysha," Abramovich told the court.

After fleeing Putin's Russia in 2000, Berezovsky claims Abramovich sought to curry favor with Putin by threatening him with expropriation unless he sold his Sibneft stake to him.

Russia's state gas monopoly Gazprom bought Sibneft from Abramovich for $13 billion in 2005. Abramovich denies any threats were made.

Berezovsky also claimed Abramovich sold his shares in RUSAL Plc, the world's top aluminum producer, without his permission. He is seeking over $5 billion for his claimed losses over Sibneft and over $564 million for RUSAL.

"There is no suggestion that anyone forced or pressured Mr. Abramovich into acting for the Kremlin," Berezovsky told the court. "He was simply happy to act to the detriment of his friend and partner in order to curry favor with President Putin."

Abramovich's lawyers cast Berezovsky as an obsessive man angry at the success of Abramovich who he believed enjoyed a similar level of clout with Putin -- Russia's paramount leader since December 31, 1999 -- as Berezovsky enjoyed with Yeltsin.

If after digesting the intricacies of Russian business practice, the judge rules against Berezovsky, his reputation as a publicity seeking former oligarch will be cemented.

But if Berezovsky wins, Putin will be cast as Russia's alpha-dog ruler whom even billionaire oligarchs such as Abramovich are so keen to please that they will betray their former partners.