An alleged rogue trader accused of losing £1.4 billion was caught exceeding financial trading limits set by managers to safeguard against big losses twice in the year before he was arrested, a court has been told.
Kweko Adoboli was "told off" after being reported by UBS colleague John Hughes in December 2010, Mr Hughes told Adoboli's trial at Southwark Crown Court in London.
But he told the jury he failed to report him for a second time when he discovered him breaking a daily limit in June 2011 because of the way the previous episode had affected their professional relationship. Three months later Adoboli, 32, was arrested after the bank lost the 10-figure sum.
Mr Hughes told the court he felt Adoboli resented his "grassing him up". he said: "I felt as though I had stitched him up. I think that maybe he didn't trust me as much (after he was reported)."
He added: "I never felt comfortable doing it in the first place and I didn't after that."
Adoboli is facing two counts of fraud and two counts of false accounting between October 2008 and last September, allegedly gambling away the money on high-risk illegal trades aimed at boosting his annual bonuses and job prospects.
The former public schoolboy, of Clark Street, Whitechapel, east London, worked with Mr Hughes for UBS's global synthetic equities division on the exchange traded funds (ETF) desk buying and selling ETFs, which track different types of stocks, bonds or commodities such as metals.
The court has heard that at one point he was at risk of causing the bank losses of 12 billion US dollars (£7.4 billion). He claims he acted with the backing of his bosses at the bank.
Mr Hughes, 30, who was sacked by UBS in the wake of the loss, grinned at Adoboli in court when asked about their long working hours.
He described his former colleague as "braver" than him and a "very, very good" trader. "I was good but I was a pain in the arse," he said. "I was prickly. Kweku was the good guy. He had a bigger risk appetite than I did."