Heather Mills is employing a team of forensic accountants to prove that her ex-husband Paul McCartney is worth more than £400 million ($800 million).

Branded a fantasist by a judge, Heather was awarded £24.6 million in a divorce settlement last week although believes she’s entitled to more.

Speaking of the singer's wealth, she said outside court: "We all know he's worth £800million. He's been worth £800million for the last 15 years."

The charity worker is now determined to prove that the Beatles star is worth double the amount he claims so that more money can be extracted from him to care for their four-year old daughter Beatrice.

One friend told the Daily Mail: "Heather says she can prove the amount of money that is being given to look after Bea will not last over the year. She is putting it to the test.

"Even with Bea travelling in economy Heather says it's not enough. She is keeping every receipt - including her invoice to her security team - to show that £35,000 is just not sufficient.

"Heather's thinking is that Bea should not be seen to have a different lifestyle when she is with Heather compared to Paul - and she is going about proving that is not possible.

"Heather is hoping Paul will discretely make a payment to her annually rather than want to go back to court and rake all this up again."