Tom Hayes, once branded the “ringmaster” of interest rate rigging, has played a central role in the unraveling of a high-profile scandal involving the manipulation of benchmark interest rates such as Libor and Euribor. His conviction, alongside those of eight other bankers, has increasingly come under scrutiny in recent years, raising significant questions about the handling of the Serious Fraud Office’s (SFO) Libor investigation and the reliability of subsequent convictions.

Hayes, a former trader at UBS and Citigroup, became the first person worldwide to be convicted by a jury for Libor manipulation in 2015. Libor, the London Interbank Offered Rate, was a key financial benchmark used to price hundreds of trillions of pounds in loans, mortgages, derivatives, and other financial products. The scandal erupted amid public outrage against bankers still reeling from the 2008 financial crisis, which had led the UK government to inject £137 billion into the banking sector.

Despite his initial guilty verdict and a 14-year sentence (later reduced to 11 years on appeal), Hayes consistently maintained his innocence, alleging no deceitful practices in his trading activities. In 2021, following his release after serving five and a half years, Hayes reiterated that his actions did not involve subterfuge. His claims gained some support from reports that the Bank of England and the UK government pressured banks to lower their Libor submissions during the financial crisis to stabilize markets.

In a landmark ruling in July 2025, the UK Supreme Court quashed Hayes’s conviction, citing misdirection by the trial judge to the jury that compromised the fairness of the trial. This decision has triggered a cascade of overturned convictions linked to the SFO’s Libor and Euribor investigations. In the past months, six additional convictions have been quashed, reflecting a wider reassessment of the legitimacy of these prosecutions. Hayes’s persistent legal challenges have been pivotal in prompting this re-evaluation.

However, the Supreme Court’s ruling stopped short of fully exonerating Hayes, noting that properly instructed juries could have found sufficient evidence of conspiracy to defraud. Nevertheless, when viewed alongside international developments, doubts persist over the foundations of these cases. In Germany, authorities ruled Euribor manipulation was not a criminal offense under national law, and French officials declined to extradite a former Barclays trader sentenced in absentia in the UK, citing similar legal gaps.

The United States, which initially convicted ten individuals for similar rate-rigging offenses, has since cleared all those accused. Within the UK, Peter Johnson, a former Barclays employee sentenced in 2014 after pleading guilty, remains the sole individual whose conviction for rate-rigging has not been overturned. Johnson’s guilty plea was influenced by concerns over legal costs and the prospect of extradition to the US. He is currently appealing his conviction, encouraged in part by the recent quashing of another guilty plea conviction—former Deutsche Bank trader Christian Bittar.

The ongoing overturning of convictions has exposed significant flaws in the prosecution and judicial handling of the Libor scandal, highlighting the complexities involved in regulating and litigating financial benchmarks. With the majority of convictions challenged or reversed, the future of the wider rate-rigging prosecutions now hangs in the balance.