A highly-placed source told The Sun: “It’s very sad. They were a great couple and brilliant parents. They just couldn’t live together any more.”
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.”