The High Court has issued an order freezing $15m of assets belonging to art collector Sheikh Saud Bin Mohammed Al-Thani.
Mr Justice Haddon-Cave issued his judgment on November 9, describing the behaviour of the sheikh, a member of the Qatari royal family, as "discreditable, dishonourable and disturbing" after he left a trail of unpaid bills at auction houses around the world.
Legal proceedings had begun against Sheikh Saud after he failed to settle a $19.7m bill in the wake of the Prospero sale conducted by A.H. Baldwin and Sons Ltd, Dmitry Markov Coins and Medals, and N&M Numismatics at New York's Waldorf Hotel in January.
The court heard that lots he bought made up 80% of the value of a market-defining sale of Archaic, Classical and Hellenistic Greek coins and his purchases included the most costly coin in the sale - a Pantikapaion gold stater, at a record price of $3.25m (£2.21m).
The sheikh accepted he had not paid any of the $19.7m he owed for the coins - a bill since swollen to $25m by interest - and had at no stage denied his liability to pay. The judge said the three numismatic dealers had an "unanswerable case" against him and said the sheikh had "absolutely no defence" and had not even suggested one.
"The explanations, excuses and unfulfilled promises given by the sheikh and/or his staff in the past few months have been unsatisfactory," added the judge, concluding that there was "more than sufficient material" to justify freezing his assets up to a value of US$15m.
The court also heard that the Prospero bill was not an isolated case as the sheikh had unpaid debts with Bonhams, Sotheby's and at least five other auction houses and art dealers. The deadlock over payment had become so entrenched that the UK ambassador to Qatar - and his opposite number in London - had become involved.
Mr Justice Haddon-Cave judge said: "This pattern of behaviour is both unexplained and inexplicable, save on the basis that it is compulsive and redolent of someone with a complete disregard for his contractual obligations. It is a serious cause for concern. The sheikh's royal status is irrelevant. We are all equal in the eyes of the law."