A trader who worked for UBS and Citigroup was jailed Monday for 14 years by a London court after becoming the first person to be found guilty by a jury of rigging the benchmark Libor interbank lending rate. The verdict on Tom Hayes, 35, came after a two-month trial at a London court. Hayes had denied eight counts of conspiracy to defraud between 2006 and 2010, when he worked for Swiss bank UBS and its US rival Citigroup. He stared ahead, emotionless, as the verdict was read out while his wife and parents sat in court with bowed heads. Prosecutors said Hayes was the "ringmaster" of more than a dozen traders who worked to rig the London Interbank Offered Rate (Libor). Libor, an estimate of the average interest rate for banks borrowing from other banks, is a key reference for many financial products around the world, from consumer loans to savings accounts. It is estimated to underpin some $500 trillion of contracts, from mortgages to the cost of corporate lending. Hayes told investigators that "influencing" Libor was "commonplace" and referred to himself as a "serial offender". Libor is calculated daily, using estimates from banks of their own interbank rates. However, the system has been found to be open to abuse, with some traders lying about borrowing costs to boost trading positions or make their bank seem more secure. Scandals over Libor rigging have affected a number of major banks, first coming to the fore in 2012 when Britain's Barclays paid £290 million (410 million euros, $450 million) to settle claims in Britain and the United States. Prosecutor Mukul Chawla had told the court that Hayes, who has a mild form of Asperger's Syndrome, set out to manipulate Libor "on an almost daily basis". "He behaved in a thoroughly dishonest and manipulative manner by repeatedly cheating those with whom he had entered into huge financial transactions," Chawla said. "The motive was a simple one: it was greed." Judge Jeremy Cooke described Hayes as "by nature a gambler". Hayes joined UBS in Tokyo in 2006, where he was paid a salary of £1.3 million before tax. He then went to work for Citigroup in Tokyo, earning £3.5 million before tax for nine months' work. He worked as a trader in yen Libor derivatives, betting on movements of the daily rate. He was arrested in December 2012 as part of a prosecution brought by Britain's Serious Fraud Office, which handles complex fraud and corruption cases. Hayes's legal costs were paid by legal aid, which is funded by the British taxpayer.