It should have been a fairytale ending when the most successful musician in pop history married a beautiful former model.

But on Monday Sir Paul McCartney faces his estranged wife, Heather Mills, across a courtroom where they will be battling to reach a divorce settlement after a marriage that lasted less than four years.

With the former Beatle's fortune estimated at £825 million, it has the potential to be the most costly divorce in British legal history.

However, unless one of the McCartneys takes issue with the settlement being hammered out behind closed doors in the Family Division of the High Court and goes to the Court of Appeal, the figures and details will never be known to the outside world.

There has been speculation amongst divorce experts based on recent big money cases suggesting that the settlement could reach £60 million, exceeding the record £48 million businessman John Charman was told to pay his former wife in May this year.

But lawyers agree there are many imponderables which could limit Lady McCartney's payout, including the shortness of the marriage and the fact that the bulk of Sir Paul's fortune was amassed decades before the couple met - she is just 40 while he will be 66 this year.

They have a three-year-old daughter, Beatrice, whose future will also figure large in the negotiations.

The venue for the hearing is a cavernous, oak-panelled courtroom where the ceiling soars more than 30 ft.

It is in the West Green section of the Royal Courts of Justice - traditional home of divorce hearings before the advent of "quickie" divorces.

The hearing concerns the financial aspects of the divorce and will be a very private affair. All the public areas of the court will be empty and the media circus attracted by the celebrity court drama must content itself with just glimpses of the couple as they arrive for the hearing - and speculation over the events inside the court.