Iceland’s supreme court has upheld convictions of market manipulation for four former executives of the failed Kaupthing bank in a landmark case that the country’s special prosecutor said showed it was possible to crack down on fraudulent bankers.

Hreidar Mar Sigurdsson, Kaupthing’s former chief executive, former chairman Sigurdur Einarsson, former chief executive of Kaupthing Luxembourg Magnus Gudmundsson, and Olafur Olafsson, the bank’s second largest shareholder at the time, were all sentenced on Thursday to between four and five and a half years.

The verdict is the heaviest for financial fraud in Iceland’s history, local media said. Kaupthing collapsed under heavy debts after the 2008 financial crisis and the four former executives now live abroad. Though they sometimes returned to Iceland to collaborate with the court investigation, none were present on Thursday.

Iceland’s government appointed a special prosecutor to investigate its bankers after the world’s financial systems were rocked by the discovery of huge debts and widespread poor corporate governance. He said Thursday’s ruling was a signal to countries slow to pursue similar cases that no individual was too big to be prosecuted.

“This case...sends a strong message that will wake up discussion,” special prosecutor Olafur Hauksson said. “It shows that these financial cases may be hard, but they can also produce results.” Not all of Iceland’s prosecutions have succeeded. But the country’s efforts contrast with the United States and particularly Europe, where though some banks have been fined, few executives have been tried and voters suffering post-crisis austerity conditions feel bankers got off lightly.

A recent scandal at the Swiss private bank of Europe’s biggest lender HSBC has highlighted the controversy again and sparked a political row about whether the bank did enough to pursue possible tax dodgers.

Reuters