Commerzbank has launched High Court proceedings against the Turkish billionaire Mehmet Karamehmet in the latest international dispute to be brought to Britain.
Germany's second-largest bank filed the case in the Commercial Court last week, according to documents seen by The Independent on Sunday.
Although it is currently unclear what the dispute is about, it is likely to attract attention as it progresses due to the fact that Mr Karamehmet was jailed in Turkey last month for embezzlement.
The businessman is one of the world's richest men with an estimated fortune of $2.4bn (£1.55bn), according to Forbes. He is best known as the founder of Turkey's largest phone company, Turkcell.
However, he was sentenced to seven years in prison by a court in Istanbul over loans issued under his watch while at Pamukbank, a private bank of which he was deputy chairman. Mr Karamehmet was previously sentenced to 11 years in 2010, although this was later overturned by Turkey's court of appeal.
Commerzbank did not return calls for comment, while Mr Karamehmet could not be reached.
News of the court filing comes just weeks after it emerged that the Ukrainian billionaire Viktor Pinchuk was suing two of his compatriots in the High Court, claiming they failed to hand over an iron ore business for which he paid $143m.
Mr Pinchuk claims he agreed to buy the factory in the city of Krivy Rih from Gennadiy Bogolyubov and a second oligarch in 2004, but they didn't transfer it after being paid.
Mr Bogolyubov said he will fight the claim.