The High Court judge imposed a gag order on Paul McCartney and Heather Mills to prevent leaks of their five-day divorce hearing, the Daily Mail reported Tuesday.

Justice Hugh Bennett warned the couple and their advisers that they face contempt of court proceedings and huge fines if confidential details of their divorce are made public.

The order was issued at the start of a High Court hearing to decide how much compensation Mills receives after four years of marriage to the former Beatle.

One Daily Mail source said Tuesday: "The judge made it clear at the start of proceedings that the hearing was being held in private and that all evidence should remain strictly confidential. All the parties in court were warned about the possible consequences of leaking information. Anyone caught revealing confidential details of the court hearing, set to last five days, is likely to be found in contempt of court and fined."

Bennett issued the warning amid intense media interest in the case. Details of a settlement may never become public unless the case goes to the Court of Appeal.

Mills, 40, is a former model whose left leg was amputated below the knee after a motorcycle accident in 1993. She became active in campaigning against land mines and in favor of animal welfare.

Mills is representing herself in court. She has also drafted David Rosen, a little-known London solicitor, as a McKenzie Friend, a layperson not normally a lawyer who can offer behind-the-scenes advice but not address the court, the Mail reported.

McCartney, 65, has assembled perhaps the strongest divorce team in the country, including Fiona Shackleton, who acted for Prince Charles in his divorce.

Unlike most British court cases, divorce proceedings are heard in private. The windows of the oak-paneled courtroom were papered over to stop prying eyes, the door plastered with signs reading "No Admittance — Strictly Private."

Even the size of McCartney's fortune is unknown. Some legal sources think it may be only $390 million, far less than the $1.6 billion give by the Sunday Times newspaper in its annual Rich List.

Press reports have suggested that McCartney has offered Mills around $50 million, and that she is seeking at least double that amount.

"Current estimates suggest that Heather is likely to receive anything from 50 million to 100 million pounds as her final settlement," said Suzanne Kingston, a family law expert. That sum is equivalent to $100 million to $200 million.

Legal experts said several factors that would be taken into account, including McCartney and Mills' 4-year-old daughter, Beatrice; the relative brevity of their marriage; and that most of McCartney's wealth was generated before he married Mills in 2002.

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The couple married in June 2002 — four years after the death of McCartney's first wife, Linda, from breast cancer. Beatrice was born in October the following year. McCartney and Mills announced their separation in 2006, and McCartney filed for divorce alleging "unreasonable behavior" by Mills.

The Associated Press contributed to this report.