She has been dismissed as simply a bubble-headed pop princess.

So when Britney Spears filed for divorce last week after two stormy years of marriage to Kevin Federline - now dubbed Fed-Ex - many assumed it would cost the 24-year-old singer a hefty chunk of her reported £65million fortune.

• Click here for the full details of Britney's fortune

But The Mail on Sunday can reveal that, far from facing financial ruin, astute Britney safeguarded her global business empire with an iron-clad 60-page prenuptial agreement, prior to her wedding in October 2004.

Britney wanted every penny protected by the pre-nup and ordered her vast legal team to draw up a list of all her worldwide assets, held in a myriad of companies including Britney Brands, BritneyFilms, Britney Online, Britney Touring, Fairy Zone Productions, One More Time Music and Britney Television.

To find out exactly how much she was worth, they gathered together hundreds of financial and tax statements. These documents have now been seen by The Mail on Sunday, and they offer a fascinating insight into the finances of a pop phenomenon.

We can also reveal that Britney even staged an elaborate sham wedding, again to protect her fortune.

The event, on September 18, 2004, in the modest back garden of a friend's house in the Los Angeles suburb of Studio City, was meant to be the "real thing" but, with Federline yet to sign the pre-nup, a proper wedding could not go ahead.

So, with the paparazzi on her case, Britney decided to stage the "fake" wedding - and drew up a watertight contract to ensure the ceremony was not legally binding.

The pair were then married for real in a secret ceremony on October 6 - after Federline had signed the agreement that banned him from making any future claim against any assets his wife had prior to their marriage.

A source linked to the prenuptial negotiations said last night: "Everyone thinks Britney is this hick from Louisiana but, in reality, she is an extraordinarily astute businesswoman who has built herself into a global brand.

A great deal of her fortune was made prior to her marriage and, when Kevin signed the pre-nup, he waived any right to any part of Britney Incorporated.

Without a prenuptial agreement Britney, who built her fortune off the back of bubblegum hits such as Oops! I Did It Again and Baby One More Time could have been forced to split her empire 50-50.

The financial statements gathered for the 2004 pre-nup list total personal cash and assets at the time worth £16.92million.

Her biggest year for earnings, according to her income tax returns, was 2001 when she made £10.2million. Current estimates put the value of her fortune now at £65m.

Britney, who has two sons with former back-up dancer Federline - 14-month-old Sean Preston and eight-week-old Jayden James - broke the news of the divorce to her husband via text message.

Laura Wasser, 37 - one of Hollywood's most ruthless lawyers - drew up Britney's pre-nup and is also handling her divorce.

Britney showed off her new slimline figure in New York last week, giggled happily during an ice skating session.

As our report reveals, her apparent relief at being free may also be down to the fact that, with her mighty fortune protected, she is still able to laugh all the way to the bank.