Ex-business partner sues Abramovich

Lawyers for the pair, who were not in court, began preliminary skirmishes over the exact form of the allegations made by Mr Berezovsky, 62.

He is suing the 41-year-old Chelsea boss over claims that he was forced to sell shares in Russian oil company Sibneft, aluminium giant Rusal and the country's central TV channel ORT at a gross undervalue after being put under duress and intimidated.

These threats included pressure from Mr Abramovich that if the shares were not sold, they would be expropriated by the Kremlin, the court heard.

But Andrew Popplewell QC, representing Mr Abramovich, told Judge David Mackie QC that the claims were "hopeless" and he would be considering making an application to have the action struck out because it had no realistic chance of success.

He said: "These are very large claims running into billions of dollars.

"But the arguability of the claims depends wholly on oral conversations which are not documented."

An application for a summary judgment striking them out was being considered, he told the judge.

The two opponents, who were once business partners, are among the richest men in the world - but Mr Berezovsky's estimated £500 million fortune is dwarfed by Mr Abramovich's £10.8 billion.

Mr Berezovsky fled to the UK in 2000 after falling out with the then Russian President Vladimir Putin.