Kweku Adoboli, the ex-UBS trader accused of losing the Swiss bank $2.3 billion, was a "star" and his desk was doing "amazingly well" in the months before the debacle, a London court heard on Thursday.
However, Christophe Bertrand, the most junior of the four traders who made up the Exchange Traded Funds (ETFs) desk where Adoboli worked, also said the alleged "rogue trader" could be unfriendly and difficult to work with.
Adoboli, 32, was arrested in September 2011, and is on trial at Southwark Crown Court accused of fraud and false accounting, charges he denies.
Bertrand told the court that as far as he was aware, the desk had made about $70 million in profits in the first half of the year, mostly from proprietary trading conducted by Adoboli and the other senior trader on the desk, John Hughes.
That compared with about $15 to $20 million for the whole of the previous year, he said.
"It (the desk) was doing amazingly well," he said. "Other senior traders would come to our desk to ask us for our advice. Everyone knew it was Kweku Adoboli and John Hughes doing the proprietary trading. They were the stars of the trading floor."
The prosecution has presented Adoboli as a "master fraudster" who routinely exceeded risk limits and masked his positions with fictitious hedging trades.
The defense has portrayed him as a hard-working team player who believed his trading and accounting methods were for the good of the bank and of his colleagues.
Bertrand said Adoboli had mentioned to him at least once in 2011 his "umbrella" but he did not have a full understanding of what this was.
According to the prosecution, the umbrella was a secret fund Adoboli used to park profits from unauthorized trades and leak them into the official accounts to plug losses.
Bertrand gave an unflattering description of Adoboli, who was in charge of training him when he joined the ETFs desk in June 2010.
"He was quite rough. One of the rules he had put in place was that I could not ask the same question twice. Quite often when I asked a question he gave me the silent treatment."
Bertrand, who is French, was asked by the judge whether he could find a better word than "rough" to describe Adoboli's attitude to him. "Unfriendly, unpleasant, superior," he replied.
It was revealed in court documents that Bertrand's fellow traders had given him two nicknames. One was "Bateman" in reference to a perceived resemblance with the main character in the film "American Psycho". The other was "FFF", an acronym for something rude which the jury were advised not to speculate on.
Bertrand's description of Adoboli was in sharp contrast to what the jury had heard from previous witnesses, and from excerpts from Adoboli's performance appraisals, in which he came across as friendly, approachable and helpful.
Bertrand testified that he was unaware of the extent of Adoboli's trading losses until he came into work on September 15, 2011, hours after Adoboli was arrested in the dead of night.
"I came into the office at around 6:15 ... I started logging on but noticed that things were missing on my desk," he said.
He sought out a manager to explain what was going on, and from that moment on he did not return to work on the ETFs desk.
Instead, over a period of weeks, he was questioned by UBS lawyers and compliance experts and by KPMG accountants who had been hired by UBS to investigate what had happened.
He was also interviewed by police under caution, and was informed of his rights as a possible suspect. He has not been charged with anything.
After UBS disciplinary hearings which he felt resulted in unfounded allegations being made that he had assisted Adoboli, Bertrand resigned from the bank in November 2011.
Unlike Hughes, who testified earlier in the trial that he had "fully deserved" his dismissal, Bertrand was clearly aggrieved about the chain of events.
The trial continues on Friday.
(Editing by Mark Potter and Elaine Hardcastle)
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