Former Barclays chief executive John Varley is due to give evidence at a High Court trial after the bank became embroiled in a £1.6 billion battle with a businesswoman.
Amanda Staveley has made complaints about the behaviour of Barclays bosses when negotiating investment deals during the 2008 financial crisis.
She says Barclays agreed to provide an unsecured £2 billion loan to Qatari investors.
But she says that loan was “concealed” from the market, shareholders and from PCP Capital Partners, a private equity firm she runs.
PCP is suing the bank and wants £1.6 billion in damages.
Barclays disputes PCP’s claim and says it is made “of sand”.
A judge is considering evidence at a trial at the High Court in London and Mr Varley is scheduled to begin giving evidence on Thursday.
Mr Justice Waksman, who began overseeing the trial on June 8, has already heard evidence from Ms Staveley and witnesses called by PCP..
Ms Staveley, who in recent months has been involved in brokering a deal which could see a Saudi consortium take control of Newcastle United, says PCP introduced Manchester City owner Sheikh Mansour to Barclays and he “subscribed” to invest £3.25 billion.
She says PCP is owed money for the work it did.