Georgian oligarch Bidzina Ivanishvili held a large equity position in an account outside Credit Suisse, the bank whose offshoot Credit Suisse Life (Bermuda) he is suing for the loss of $400 million over a call for payment for the same high-risk equity.

The evidence was introduced during the fourth week of the case, which has pitted Mr Ivanishvili, who is also the former leader of the Caucasus nation of Georgia, against the Bermuda-based life insurance company.

Mr Ivanishvili received the $400 million call for leveraged shares in a drug development company called Raptor Pharmaceuticals.

The shares were held largely in the former prime minister’s Credit Suisse Life (Bermuda) policy accounts. He has vehemently denied authorising the size of the position held in his policy portfolios.

Steven Thompson, QC, spent Monday and most of yesterday cross-examining accountant David Morrey, an expert witness for Mr Ivanishvili, who explained that he had analysed documents relating to life insurance company policy accounts for which Mr Ivanishvili was the holder.

Mr Morrey wrote five reports about the complexities of the case which involve a large tranche of the former leader’s fortune.

Yesterday the accountant was asked to look at another account, this one in the international bank Coutts, which held assets representing tens of millions of dollars of Mr Ivanishvili’s wealth including Raptor shares.

There was evidence that the average percentage of assets that Raptor represented in the Coutts account was 10.8 per cent.

During the time the accountant was asked to review, the percentage of the total holdings represented by Raptor fluctuated and was 3.7 per cent at its minimum, while the maximum was 28.4 per cent.

Mr Morrey said the maximum percentage of 28.4 was not because of additional Raptor shares being added to the portfolio, but because many of the other equities were taken out of it.

The shares in Raptor were left in place, so with the withdrawal of other assets, they rose as a proportion of the portfolio.

Mr Morrey agreed with the lawyer that the account was overexposed in Raptor shares. He called it “a high-risk entity” but added that he would not object to it being held in sensible proportions in the policy accounts.

On Monday the lawyer focused on Mr Morrey’s opinion of the amount of investment risk the tycoon was prepared to take.

It emerged during questioning that documentation provided to Mr Morrey did not give him a “golden source” of the relevant data. A golden source is defined as a single, well-defined version of all the data entities on an organisational ecosystem.

The accountant repeatedly criticised the information with which he was provided, once telling the court, “I’m trying to cross a number of unideal sources”, adding that there is no document with a “clear statement of intent”.

He said he drew his conclusions based on the documentation that was available.

In further testimony, Mr Morrey described an investor’s financial position as mainly circumstantial. “It doesn’t tell me anything about their intended risk profile,” he said.

As well as being a former leader of Georgia, Mr Ivanishvili is described as an oligarch, making his fortune after the fall of the Soviet Union, ultimately becoming a billionaire and one of the world’s richest men.

Mr Thompson asked the accountant why his earliest report does not include Mr Ivanishvili’s income, his wealth or requirement for liquidity.

He responded that in his evidence “I acknowledge that the first plaintiff and his family are high net worth individuals and would have the ability to take on a high level of risk.”

He also acknowledged they are not dependent on the return on their investments to maintain their lifestyle.

But he said: “There is a fundamental difference between an individual’s ability to sustain an investment loss versus the actual objectives they wish to see the portfolio managed to.”

The case continues.