£200m: The gloves are off. McCartney versus McCartney has begun

They wanted the divorce to be amicable, but now the lawyers are involved. The first blows have been landed in the big money fight. By Cole Moreton

The wedding ring is off. The dazzling team of lawyers is in place. Sir Paul McCartney has filed for divorce, it emerged yesterday, and the publicly genial former Beatle seems to be preparing for a long, tough battle with his estranged wife, Heather.

Both had hoped for an amicable split, for the sake of their two-year-old daughter, Beatrice. But yesterday a friend revealed that Sir Paul's petition for divorce had been submitted to the courts and it blamed the break-up of the four-year marriage on Lady Heather's "unreasonable behaviour". The singer was said to have described his wife as "argumentative" and "rude to staff".

Lady Heather hit back by saying she would be filing counterclaims in British and American courts, putting her own side of the story. A court battle on both sides of the Atlantic could take more than a year. The former model turned charity campaigner might emerge with a £200m settlement - but her lawyers will have to beat one of the most impressive legal teams ever to contest a British divorce. It includes Fiona Shackleton, the tough divorce specialist who helped Prince Charles part from Diana, and Nicholas Mostyn QC, whose results in high-profile divorce cases have earned him the nickname Mr Payout. Leading them from behind the scenes will be John L Eastman, long-time lawyer, manager and friend of Sir Paul - and the brother of his late wife Linda.

Sir Paul, 64, waved cheerily to photographers at his Liverpool Institute of Performing Arts on Friday, but they noticed that his ring finger was bare for the first time in four years. His hair was a more natural, greying colour and his clothes more formal than they have been during his marriage.

"Paul just wants to get this over as quickly and cleanly as possible and put the whole sorry episode behind him," his friend was quoted as saying in the Daily Mirror yesterday, while giving details of the divorce petition. But in The Sun "a source close to the family" said the singer was furious. "He was determined these details would remain private, and he's very disappointed that someone in a position of trust has revealed all."

Meanwhile a statement released by Lady Heather, 38, said she was "hugely disappointed that matters of such a confidential nature should be aired in public and feels it inappropriate to speak about such delicate matters when a child is involved."

Lawyers for both sides will try to agree a compromise in private - but if they cannot do so then the secrets of the brief McCartney marriage may well be aired in a public court room, including the hostility apparently felt towards Lady Heather by her stepchildren. This became more public earlier this month with the news that someone had bugged the line at Sir Paul's home in East Sussex, recording a conversation in which his daughter, the 33-year-old fashion designer Stella McCartney, gave full vent to her feelings, claiming, among other things, that her stepmother had lied about her past.

Sir Paul was embarrassed at the conversation and angry at the breach of security. However, the claims he discussed with Stella have also been reported in the tabloid press, which said Heather Mills once posed for pornographic pictures in a German sex manual. It also said she once worked as a prostitute among wealthy Arabs. Lady Heather strongly denies this and has threatened to sue when the divorce is settled.

Sir Paul is worth an estimated £825m, thanks to his career with the Beatles and as a solo performer, plus his property and publishing companies. His marriage to Linda Eastman lasted from 1969 to her death from breast cancer in 1998. They had three children, and he adopted her daughter by a previous marriage.

A year after Linda's death, Sir Paul went to a charity function and met Heather Mills, a 31-year-old model famous for going on working after losing part of her leg when she was hit by a police motorcycle. She was a campaigner on behalf of amputees, knew how to handle publicity and, like all the McCartneys, was passionately against cruelty to animals.

Their romance was hard for the McCartney children to accept, but received the blessing of Linda's brother John. The couple were married in 2002, at the remote Castle Leslie in County Monaghan. There was no pre-nuptial agreement.

HIS LEGAL TEAM

Heather Mills McCartney has yet to name the lawyers who will represent her in British and American courts, but reports suggest Sir Paul has his legal team in place.

John L Eastman 69

The brother of Sir Paul's late wife Linda has been his lawyer-manager since helping to dissolve the Beatles in 1970. Runs McCartney Productions, a publishing company with rights to the songs of Buddy Holly and musicals including Grease. Leading Apple Corps' legal fight against Apple Computer. Clients include Andrew Lloyd Webber and David Bowie.

Fiona Shackleton 50

Known as the Steel Magnolia for her toughness, this divorce specialist says: "It helps to have a rod of steel through your back and loads of charm." Represented Prince Charles, persuading Diana to give up being called Her Royal Highness in return for £17m. Personal solicitor to Princes William and Harry.

Nicholas Mostyn QC 49

Charges £500 an hour but gets results to justify his nickname Mr Payout. Helped Karen Parlour, the wife of former England footballer Ray Parlour, win half her ex-husband's future earnings, a landmark case. Won £5m for Melissa Miller after three years in a childless marriage.