Heather Mills set to claim Paul McCartney was "violent" towards her

Heather Mills and Paul McCartney are set to take the witness box tomorrow - and Mills has made a vow to expose Paul's "violent past".

Mills, dubbed Mucca by British tabloids due to her porn past, is determined to dish the dirt after failing to thrash out a divorce deal with the Beatles legend.

Sources claim Sir Paul, 65, has already rejected her demand for a $20million kiss-off.

And now, the High Court will decide how much of Paul's estimated $1.6bn fortune Heather Will get.

Talks to agree an out-of-court deal fell through after the embattled couple clashed over how a cash settlement would be paid.

The former 'Beatle' - who denies being violent - insists on a gagging order to stop Heather publicly revealing details about their four-year marriage.

He also wants any payments to be spread over the next 14 years - when their daughter Beatrice will be 18.

But Heather refused to be gagged.

Heather - who celebrated her 40th birthday last month, is urging judge Mr Justice Bennett to take the rare step of hearing the case in open court so her claims about her husband's brutality can be reported.

She also hopes it will cajole other "victims" of domestic violence to come forward.

A source said: "Heather wants to make the history of their relationship public.

"She has continually said she wants to reveal her husband's violent past.

"The public's negative perception of her has been a constant source of distress to her and she hopes going down this route will change that."

Heather - Paul's second wife - with whom he has one daughter, Beatrice, is set to represent herself at the week-long hearing after ditching her lawyers. The move means she can force Sir Paul to go into the witness-box and be cross-examined by her.

Legal experts have warned that accusing Macca of violence was a huge risk. "If the judge finds there's no truth in malicious allegations, it could massively reduce her settlement, said top divorce lawyer Vanessa Lloyd-Platt, who's not involved with Mills/McCartney divorce.

"And Paul will have every right to say, ' You have bandied about false allegations that have affected my reputation, my records, my future and my image.'

"He will then be able to counter-claim - and she could be left with a lot less than she hoped for."

Heather hopes the court will order Sir Paul to pay her a lump sum settlement.

But Macca fears she would then sign a megabucks kiss 'n' tell book deal - and wants to stagger the money to buy her silence.

A source told Britain's Sunday People newspaper: "His people have talked about amounts around the $5million-a-year mark until Bea is 18.

"By then he will be 80 and what Heather has to say will be irrelevant."

And a pal said: "Paul is increasingly frustrated with Heather's erratic demands and wants it settled now.

"But he is determined not to give in to anything he is not happy with.

"The problem is Heather is just as stubborn - so it looks set to be a long week."

Experts said the judge is likely to concentrate on working out how much Heather and Bea need if they are to carry on enjoying the lifestyle they now have.