The deal maker, Amanda Staveley, is taking steps to sue Barclays for its role in raising £3.5 billion from Qatar as part of the total of £7 billion deal from Middle Eastern investors to bail out the troubled bank.
Ms Staveley acted for Abu Dhabi, which provided the remaining £3.5bn to help keep Barclays out of a UK taxpayer bailout in 2008.
But the Qatari side of the deal is now the subject of an investigation by the Serious Fraud Office into a £322m fee Barclays allegedly paid to a third party in Qatar to secure its investment.
"The whole thing has been a nightmare," she told Porter magazine. "Especially when you feel like you've done an exceptional deal. The last thing I thought was that Barclays would pay Qatar an additional sum of money. Instead of calling it a fee, they said that Qatar was advising them. But Qatar has done nothing wrong – the FCA is investigating Barclays; not Qatar or me. The matter is in the hands of our lawyers and we have appointed a QC to represent us in litigation against the bank.'"
The FCA said it is minded to fine Barclays £50m over the affair and the SFO is investigating.
Now a multimillionaire, Ms Staveley also told of how she had once been homeless, sleeping "in the doorway of a bank in the City of London" for a night when a deal went wrong, leaving her penniless. Cambridge and boarding school educated, she had been too proud to ask her landowner father for help.
She recalled from her childhood: "My father was very clear: I was from an old Yorkshire family and Yorkshire families stay together and the inheritance goes from father to son, and that could never change. So I knew I had to make it on my own."
She suffered through university with a melancholy that had persisted from childhood, resulting in her being admitted to hospital with anorexia: "It was a dismal, dismal time."
Ms Staveley also revealed that businessmen had offered her "a lot of money" to become their lover, saying: "But I couldn't go through with it. I cried my eyes out because I couldn't do it. It must be the most horrific thing in the world to sell your body."