McCartney, Mills Hire Royal Lawyers
McCartney, 64, has hired Prince Charles's former lawyer Fiona Shackelton, while Mills, 38, has retained solicitor Anthony Julius, who won Diana a reported $30 million settlement, according to the BBC.
Mills and McCartney separated in May after nearly four years of marriage. They have a 2-year-old daughter, Beatrice Milly.
According to reports, Mills is believed to be seeking a settlement of $500 million from McCartney, whose wealth has been estimated to be close to $2 billion.
Mills's spokesman Phil Hall confirmed press reports that McCartney had frozen the couple's joint bank account and sent a "legal letter" to his estranged wife, complaining that three bottles of cleaning fluid were taken from his Sussex, England, home to clean her local office.
"She feels let down. Her friends feel his side is trying to crush her in the hope that she will take a low settlement when the divorce happens," a Mills pal tells PEOPLE.
Meanwhile, McCartney's camp insists the former Beatle is being made out to appear mean. "She paints herself as a victim, but this is not true," an insider tells PEOPLE. "There's a lot of careful orchestration going on."
Meanwhile, on Monday police were called to McCartney's London residence when Mills's security guard climbed over a wall to let her in. The locks on the gates had been changed.
Although the couple initially described their separation as amicable when it was announced in May, McCartney cited her "unreasonable behavior" in divorce papers and Mills responded by vowing to file counter-claims in Britain and the United States.