A Nigerian politician who was jailed in Britain for laundering tens of millions of dollars in stolen public funds through British banks and properties lost an appeal against his conviction in London on Wednesday.

The Court of Appeal’s ruling against James Ibori, a former governor of oil-producing Delta State in southern Nigeria, is a relief for the British authorities at a time when they are trying to stem the flow of dirty money from overseas through London.

Ibori, who in his heyday was one of Nigeria’s most powerful men, pleaded guilty in a London court in 2012 to 10 counts of fraud and money-laundering involving sums amounting to at least 50 million pounds ($66 million).

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He received a 13-year jail sentence of which he served half, as is common in the British system.

Anti-corruption campaigners had hailed the case as a milestone for Nigeria, where no one of his statures had been successfully prosecuted, and for its former colonial ruler Britain, long seen as too complacent about the proceeds of Nigerian corruption being laundered on British soil.

Despite his guilty pleas, Ibori, who is now back in Nigeria, appealed against his conviction alleging that one of the London police officers who had investigated him was himself corrupt and that the prosecution had covered that up.

Three senior appeal judges said the corruption of the police officer was not proven but in any case, it was irrelevant to Ibori’s conviction because if it had happened, he had instigated it.

“If (the policeman) was corrupt, Ibori was the instigator or at the very least intimately involved in any such corruption,” their written ruling said.

“Regardless of any disclosure failures on the part of the Crown (prosecutors), Ibori was thoroughly informed on this topic prior to his pleas of guilty.”

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The ruling will allow British prosecutors to resume efforts to confiscate tens of millions of dollars’ worth of assets and return them to Nigerian public coffers. The assets have been frozen for years while the case has been dragging through the courts.

During his eight years in office, Ibori enjoyed a jet-setting lifestyle, buying multi-million dollar properties in England, South Africa and the United States as well as a Bentley, a Jaguar and other luxury cars. At the time of his arrest, he was in the process of buying a $20-million Bombardier private jet.