(Bloomberg) -- Veteran trader Guenther Klar lost his fight to avoid extradition to Belgium, where he’s wanted for questioning in the country’s investigation into tax fraud.

He would be the first trader extradited from the U.K. to another country as part of a probe related to controversial Cum-Ex trading. Prosecutors want to question the 51-year-old in relation to an alleged 22 million-euro ($26.7 million) fraud, according to court documents.

Klar “is said to have been the main orchestrator (playing a ‘leading’ role) of the scheme whereby very substantial withholding tax re-claims are said to have been unlawfully made,” Judge John Zani in London said in a ruling Thursday.

At least three countries, Belgium, Denmark and Germany, are seeking the extradition of London financial professionals related to Cum-Ex strategies. Prosecutors say investors illegally made billions of euros by rapidly trading shares to obtain multiple refunds on dividend taxes paid only once.

Kevin Robinson, a lawyer for Klar, said he will appeal the ruling. He has 10 days to file any objections and Klar remains on bail.

Robinson said before the ruling that Klar “is not the subject of any prosecution or similar process in Belgium” and that the only purpose behind the extradition request is to conduct an interview.

Read more: Hedge Fund Trader Faces Extradition to Belgium Over Cum-Ex

Klar has “already provided hundreds of pages of documentation demonstrating the true nature of his trading activities” and his offer to be interviewed was declined, Robinson said.

The Belgian tax probe isn’t limited to Klar and involves losses of 208 million euros in total, the country’s tax agency said in an email.

Cum-Ex was a trading strategy that used the rapid trade of shares to gain duplicate tax refunds. The practice, named for the Latin term for “With-Without,” took advantage of how dividend tax was collected under laws that seemed to allow multiple investors to claim refunds on a dividend that was paid only once.

Klar was arrested under a European Arrest Warrant while boarding a flight from Manchester airport in June 2019, according to court documents. Belgium alleges in the arrest warrant that Klar’s acts took place from June 2012 to May 2016.

He worked at Sanjay Shah’s Solo Capital hedge fund from 2010 through 2012, according to a U.K. Financial Conduct Authority database. Klar had worked at Royal Bank of Scotland Group Plc for a number of years before that.

(Updates with Belgian tax authority comment in ninth paragraph)

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