… The source said: “Despite huge attempts to patch things up they both knew deep down that divorce was on the cards.
“It wasn’t a matter of ‘if’ but ‘when’. They tried hard over the last few months but their fighting was getting out of control.
“The final straw came before Madonna started her US tour.
“Madonna wanted a highly stage-managed separation, with their split being announced when it was convenient for her.
“She didn’t want the distraction while she is trying to concentrate on her tour.
“But a series of rows around Guy’s 40th birthday last month were so bad that Madge ended up storming out of the house and Guy’s had enough.
“Guy said if they were going to split, it has to be now — and their marriage will finally be over in a matter of weeks.
“Madonna was dithering at first about whether a separation would be best or whether to go ahead with the divorce.
“She has now agreed with Guy that a divorce is the best thing to do.”
Guy has flown back from France, postponing filming of his new movie Sherlock Holmes, to break the news to his parents.
This week he will take his possessions from the couple’s London home, which Madonna owns, and move into their Wiltshire home, which he owns.
Madonna — in New York on Monday night for the premiere of her new movie Filth And Wisdom — initially planned to move back to the US with their three children in July.
The source said: “She was adamant that she was leaving Guy and not coming back.”
But talk of the separation leaked out — along with rumours that Madonna was secretly seeing a married baseball star — and Guy flew out in a public last-ditch bid to repair the marriage.
The Sun led the way in reporting the couple’s ups and downs.
Madonna instructed her spokeswoman to put out a strongly-worded statement insisting there were “no plans” to divorce.
And the couple put on a show of unity at the UK premiere of Guy’s film RocknRolla, at Madonna’s birthday party and then at his birthday bash.
They also shared a weekend in Italy. It was planned as a romantic break but ended with them sleeping in separate rooms.
The source said: “Lately Guy has been putting his foot down about a lot of stuff.
“He is sick of his career taking a backseat to hers and was determined to spend as long as he had to promoting RocknRolla here, even if it meant being away from Madonna rehearsing in the US.”
They went on: “When Madonna first moved to the UK, she loved the idea of becoming an English rose. But slowly it turned sour. She decided she hated hunting and quickly dropped her ‘hobby’ of going for a pint of bitter with Guy in the local pub.
“She doesn’t have many friends here and as she has turned 50 she has become very philosophical and started wondering what it’s all about.”
Other arguments raged about their kids Lourdes, 12, Rocco, eight, and David Banda, two.
The source said: “Guy wants Madonna to stop uprooting them and let them stay in one place.
“It doesn’t help that Lourdes has decided she wants to spend more time with her real father, Carlos Leon, in New York.
“Guy is very keen for Lourdes to have a good relationship with him, but it means Madonna can use that as an excuse to spend more time in America.”
Dancer Carlos has been living in Madonna’s New York apartment for the last few months, overseeing renovations in preparation for the star’s return. During that time they have rekindled a close relationship.
Madonna and Guy have also rowed about her desire to adopt another baby.
Guy did not want to adopt initially because of his own family’s experiences.
His mother Lady Amber Leighton was forced to give up a baby boy for adoption when she was an unmarried 17-year-old, and his stepmother Shireen Ritchie struggled for years to find the truth about the adoption of her mother.
Guy was persuaded by Madonna to adopt David Banda but has since resisted her pleas to adopt a baby girl.
The source said: “Guy adores David and is glad they went ahead with the adoption. But he doesn’t want to adopt another child when their marriage is rocky. It’s a real bone of contention.
“Everyone agrees it is unfair on the children to witness such terrible arguments and so the divorce has been agreed.”
Last night a spokeswoman for Madonna declined to comment.
And as Guy’s dad John left his Chelsea home with Guy’s sister, he refused to answer questions about his son.
Guy’s sister said: “We are not going to say anything today.”