A former public schoolboy accused of Britain’s biggest bank fraud “tore up the rules” as he carried out reckless trades, a court has heard.

Kweku Adoboli, 32, allegedly gambled away �1.4billion in “off-book” operations while working for UBS in London during the global financial crisis.

The banker, of Clark Street, Whitechapel, has told jurors at Southwark Crown Court that his senior managers were aware of what he was doing and encouraged him to assume riskier positions.

Coupled with the “burn-out” he was suffering during market turbulence last year, this led to a loss of control over his trades, he claims.

But prosecutor Sasha Wass QC, cross examining Adoboli today, told the court that he was trying to make the evidence as unclear as possible to the jury.

Cross-examining the defendant, she said: “You played God in that bank, tearing up the rules and doing whatever you wanted. Rules were for other people, that was your attitude.”

“Your motivation was about your reputation, your ego and your desire to be a star trader.”

He replied: “It’s got nothing to do with me, it was all about the organisation. It was because of loyalty to UBS that I worked so hard.

“The reputation, well, it comes with the territory. I don’t have a reputation to talk about.”

Adoboli, of Clark Street, Whitechapel, east London, worked for UBS’s global synthetic equities division, buying and selling exchange traded funds (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 (�7.5 billion).

In January 2008, Adoboli received an email from his employers warning supervisors about record losses incurred by French bank Societe Generale due to convicted rogue trader Jerome Kerviel.

It explained that Kerviel, who worked in the same equities markets as Adoboli, exceeded his trading limits and concealed his actions through “elaborate fictitious trades”.

Asked what he had learned from this email, Adoboli said: “We learned that we needed to ensure not to lose money.”

He described the message as a “tick-box exercise” by UBS and said that despite the warning, he was later encouraged by his bosses to push the boundaries in search of profit.

He denies two counts of fraud and four counts of false accounting between October 2008 and last September.

The trial continues.