LONDON, October 5 - RAPSI. Roman Abramovich largely owes his purchase of the Sibnet oil giant to Boris Beresovsky. However his involvement, while crucial, was limited to providing political patronage and introducing Abramovich to banks, Jonathan Sumption, QC for Abramovich, said on Tuesday at the High Court of Justice in London, RIA Novosti reported.

Abramovich did not have to pay Berezovsky and his business partner Badri Patarkatsishvili $1.3 billion for their services as Abramovich had no evidence of any obligations to them, noted Sumption.

According to the lawyer Berezovsky started to insist on his participation in Sibneft when it became profitable and Berezovsky with Patarkatsishvili received about $490 million from Abramovich in 2000.

The court will hear the witnesses' testimonies on Thursday. Berezovsky will be the first.

Berezovsky claims in his lawsuit that Abramovich intimidated him and Patarkatsishvili into selling a number of assets including a 43-percent stake in Sibneft, a major Russian oil company, and a stake in the Rusal aluminum group for significantly less than their value.

The claimed amount constitutes the difference between the price and the market value.

British mass media have calls the dispute the legal battle of the year.