When Katy Perry wed Russell Brand in 2010, everyone wondered how a sweet young pop star could tame one of the showbiz world’s most notorious bad boys. But according to those closest to the couple, the problem that led to their shock divorce announcement late last month was quite the opposite – Katy, 27, wanted a life of wild partying, while Russell, 36, was the one who wanted to settle down and start a family.

“Katy needs to realise she brought this on herself,” reveals a fellow chart-topping singer who counts Katy as a close friend. “She’s been partying nonstop ever since she married Russell and she needs to calm down.”

Speaking exclusively to Woman’s Day on condition of anonymity, the pop star explains, “Katy is so paranoid that she is going to fall out of the limelight and is obsessed with being ‘the next Madonna’. Her life is a 24/7 whirlwind of social climbing and fame chasing. She’s partying with other celebrities until four in the morning every day of the week, whereas Russell would prefer a quiet dinner party or a date night for just the two of them. It’s a recipe for disaster.”

When Katy married the flamboyant comedian, who has confessed to heroin and sex addictions, she thought she had found her “partner in crime” – someone to fuel her wild, rebellious side. But to her horror, a now-sober Russell has spent the past 12 months trying to convince Katy to tame her behaviour. Last November, he even told Ellen DeGeneres, “I am very much looking forward to being a dad – soon I hope.”

Read more about the issues that have sparked furious rows between the couple and who will come out on top in the divorce settlement in this week's Woman's Day on sale January 9, 2012.