The Court of Appeal decides today whether the ''secret wife'' of the late King Fahd of Saudi Arabia can keep a multimillion-pound award handed to her by a controversial judge.
Palestinian-born Janan Harb, 68, won a package of cash and property worth over £20 million last November.
Mr Justice Peter Smith, sitting at London's High Court, accepted her assertions that Prince Abdul Aziz, son of the late king by another wife, had agreed to the huge payout.
Lawyers for the prince are asking the appeal judges - Lord Dyson, Master of the Rolls, sitting with Lord Justice Moore-Bick and Lord Justice McFarlane - to quash the ''unsustainable'' award.
Ms Harb says the prince entered into the agreement to ''buy her silence'' over her relationship with his father.
She says the agreement was reached when the prince met her at the Dorchester Hotel in London on June 20 2003, while the king was seriously ill.
The prince denies her claim.
But Mr Justice Smith ruled that, although her behaviour was ''unattractive'', Ms Harb was ''telling the truth'' about the agreement.
He declared she was entitled to £12 million, plus interest, and two luxury flats in Chelsea, south-west London, worth around £5 million.
Lord Grabiner QC, for the prince, said Mr Justice Smith failed to analyse the evidence properly.
The judge also wrote a ''shocking letter revealing possible bias'' against Blackstone Chambers, the legal chambers which provided the barristers representing the prince.
Lord Grabiner QC said the letter was prompted by a newspaper article by Lord Pannick QC, a member of the chambers who appeared for the prince at an early stage in the Harb case.
Lord Pannick's article criticised the judge's handling of an unrelated case involving British Airways, in which the judge recused himself after demanding to know what had happened to his own luggage on a flight home from Florence.
Lord Pannick had written that the case ''raises serious issues about judicial conduct that need urgent consideration by the lord chief justice....''
In response, the judge wrote to Anthony Peto QC, one of two heads of Blackstone Chambers, saying: ''The quite outrageous article of Pannick caused me a lot of grief and a lot of trouble.''
He added: ''I will no longer support your Chambers please make that clear to members of your Chambers. I do not wish to be associated with Chambers that have people like Pannick in it.''
Lord Grabiner told the appeal judges the ''shocking and indefensible'' letter was clear evidence of possible bias against the chambers and could have affected the outcome of the Harb case.
There was also a real possibility that the judge became biased against the prince after he failed to attend court in person to give evidence.
Charles Hollander, QC, for Ms Harb, argued the appeal should be dismissed.
He said the judge had been entitled to reach a judgment in favour of Ms Harb on the evidence before him and there was lack of any real evidence of bias.
Mr Justice Smith has agreed ''to refrain from sitting'' pending the outcome of the appeal.
And the Judicial Conduct and Investigations Office (JCIO) has been investigating the British Airways matter.
Ms Harb had told the judge she was aged 19 when she married King Fahd in a secret ceremony under sharia law in March 1968 at the Al Sharafiya Palace.
But members of the king's family were opposed to their relationship because she was from a Christian family in Palestine, and she was banished from Saudi Arabia in 1970.
Both she and the king later remarried. However she told the court he had promised to to look after her for the rest of her life.