THE best sex of Brad Pitt’s life may soon be a thing of the past.

Author who predicted the Brangelina break-up said in an interview that the celebrity couple are definitely 'estranged', amid more reports that there is no truth to the latest rumour about their relationship.

In his book, Brangelina: The Untold Story of Brad Pitt and Angelina Jolie, US biographer Ian Halperin wrote: “Brad had never had such incredible sex. My sources say that they sometimes spent 18 to 20 hours a day in bed.”

But Ian Halperin, said his sources told him they have 'split romantically' and 'they kept it quiet because they want to work out something conducive to the wellbeing of the children, and I think that's a commendable way of dealing with it'.

News Of The World last weekend said the Hollywood golden couple have drawn up papers with a lawyer to officially end their five-year relationship. The split deal was said to be up to £205 million ($465m).

The unmarried couple – who said they would marry only when US homosexuals were also able to marry – have legally agreed to equally divide their vast fortune and to share custody of their six children.

According to legal papers secretly signed by the couple this month, Pitt and Jolie will get joint custody of the kids, but they will all live full-time with their mother, a source told News of The World.

Preparations for a split began early last month when the couple visited a top Los Angeles divorce firm, considered to be “the best in the business” to begin thrashing out the deal.

Mr Halperin said the sex was not enough to keep the couple together.

He said: “Sex eventually wears off. She has brought a lot of good things to him – the children, for example. But he didn’t know what he was getting into and that’s why I think they’re going to split.”

An announcement of their separation is expected to be made soon - ending months of speculation that the five-year relationship is on the rocks.

A source told News of The World: “The contract was like a tailor-made version of a pre-nuptial agreement except (it’s) for an unmarried couple’s split. It seemed clear they want the world to know they’ll both play a part in the upbringing of the children.

“There’s no date for when the contract would come into effect. But the paperwork is already organised for a break-up and for it to be as unmessy for them as possible.

“It is clear it’s a case of when they break up rather than if.”

Associates of both actors declined to comment to reporters, with one of them saying that it was a “private matter”.

Staged an intervention

The National Enquirer reported that the couple had a row at a New York restaurant called the Alto on 6 Jan.

The magazine claimed that Pitt staged the six-hour dinner as an intervention to persuade Jolie to get psychiatric help.

It alleged she had been suffering from depression since her mother died from ovarian cancer three years ago, after which her weight has dropped dramatically.

The magazine claimed Jolie had also previously attempted suicide.

According to the Enquirer, after that stormy night, the couple agreed their relationship was over and “their focus is now on making a smooth transition for their children”.

The troubled couple have not been photographed together in public in recent days.

Rumours have been circulating for months that the couple’s relationship is doomed.

On Friday night, Pitt, 46, was photographed backstage at the Hope For Haiti concert in Los Angeles without Jolie, 34. His ex-wife, Jennifer Aniston, was there, but she was not with him.

Earlier this month, Jolie was photographed looking tense with an unsmiling Pitt in New York.

Last month, she told German magazine Das Neue that fidelity was over-rated – and it would not be a problem if either of them had an affair.

She said: “Neither Brad nor I have ever claimed that living together means to be chained together. We make sure that we never restrict each other.

“I doubt that fidelity is absolutely essential for a relationship. It’s worse to leave your partner and talk badly about him afterwards.”

She also added that “the sparks fly at home” if Pitt did not see that he was in the wrong and acted defiantly.

She said: “Then I can get so angry that I tear his shirt.”

Last week, the couple did not turn up at the Golden Globe Awards although Pitt’s film Inglourious Basterds was nominated in several categories. Instead he went to watch a game of American football team New Orleans Saints, while Jolie stayed in California.

Pitt also bought the mansion next door to the couple’s Los Angeles home for £800,000 at about the same time.

The couple, who fell for each other when they acted together in Mr and Mrs Smith in 2004, have three adopted children aged 8, 6 and 5. They also have three biological children – a daughter, 3, and 17-month-old twins.

This article was first published in The New Paper.