A Saudi prince has been ordered by the High Court in London to give evidence in a multi-million pound legal battle with a woman who says she was secretly married to his late father.
If he does not attend he could force contempt proceedings - and possible arrest if he enters the UK, a judge warned.
The judge made the order even though he was told that Prince Abdul Aziz - son of the late King Fahd - has been "forbidden" by the current King Salman - his uncle - from flying to the UK to appear in the witness box.
The judge was told there were fears of the Saudi royal family being caught up in "a media circus", but he said he would ensure that did not happen.
Prince Aziz wants to rely on witness statements signed by him, and witnesses called on his behalf, to put his side of the case.
Lawyers for the prince said it was impossible for him to attend because of the stance being taken by the royal household.
But Mr Justice Peter Smith said: "I do not accept at the moment that if I make an order he will not attend."
The judge warned that if the prince failed to appear in court on Monday next week at 10am it was possible that he would be in contempt of court.
The judge added it was "equally possible" that an arrest warrant might be issued against him - "and if that happens he will be liable to arrest if he enters the jurisdiction (of the English courts)".
The judge made his order on the first day of a claim being made by Janan Harb, who is in her 60s, that she was secretly married to King Fahd - then a prince and minister of the interior of Saudi Arabia - in 1968 when she was 19.
Ms Harb, who was in court to give her own evidence, claims that she and Prince Aziz, the son of another wife of the late king, had a meeting at the Dorchester Hotel in London in the early hours of June 20 2003.
She says the prince entered into a binding agreement to pay her £12m and transfer back to her two flats in Pier House, Cheyne Walk, Chelsea, London, in order to satisfy promises given by his father to provide for her financially for the rest of her life.
The judge said the prince denied her claim, and "the lynchpin" of the case was "who do I believe?"
The way to obtain "best evidence available to decide who is being truthful" was by way of oral testimony and cross examination.
"The best way in which (the prince) can present his case is to come and tell me in person in the witness box what he says his case is."
The judge gave assurances to the Saudi royal family that the case would be handled in such a way as to prevent irrelevant "salacious and pejorative" allegations about the family being made in open court.
He said: "I will ensure that will not happen. There will be no media circus."
Later, the judge amended his order to say that the prince should attend court on Tuesday - the day he is actually likely to give evidence if he agrees to enter the witness box.