Keith Urban’s ‘cocaine clause’ could see him walk away with millions after Nicole Kidman divorce

An unusual clause in Nicole Kidman and Keith Urban's pre-nup could see Urban walk away from the relationship with millions.

It was revealed this week that Kidman has filed for divorce from Urban after nearly 20 years of marriage.

Court documents cite the reason for the split as 'marital difficulties and irreconcilable differences'.

The pair married in 2006 and have two children together, with the marriage being Urban's first and Kidman's second after her previous relationship with Misson Impossible star Tom Cruise.

They took out a prenup before the marriage, laying out the terms of any separation in the future, which has now come to pass.

But it's the 'cocaine clause' in the agreement which could see New Zealand native Urban walk away with substantial payments... so, how does it work?

Nicole Kidman and Keith Urban will soon divorce after almost 20 years together (Michael Buckner/Penske Media via Getty Images)

As reported by Radar Online, this clause states that if Urban remains sober from drugs and alcohol throughout the marriage, and if it were to end, then he would receive a payment of $600,000 for every year that they were together.

They married in 2006 before filing for divorce this year, meaning they've spent 19 years together.

A quick bit of maths reveals that it adds up to some $11.4 million in payments from the 'cocaine clause'.

Urban has spoken openly in the past about his struggles with addiction.

An interview with Oprah Winfrey saw the musician reveal that Kidman and some close friends staged an intervention shortly after their wedding, something he attributes to saving his life as it helped him to get sober.

News that the couple intend to separate has shocked the world, as many had considered them to be one of the most enduring marriages in show-business.

A clause in their prenup reveals Urban will be entitled to payments from Kidman on the condition he remains sober (Karwai Tang/WireImage/via Getty)

Court documents reveal that there are also arrangements in place about custody of their children, as well as a 'permanent parenting plan'.

It states: "The mother and father will behave with each other and each child so as to provide a loving, stable, consistent and nurturing relationship with the child even though they are divorced."

It added: "They will not speak badly of each other or the members of the family of the other parent. They will encourage each child to continue to love the other parent and be comfortable in both families."

Under this plan, Kidman will be the main residential parent for the couple's two daughters. This means that she will have them for 306 days each year, and Urban will have custody of them for the remaining 59 days.

As both parents, unsurprisingly, earn over $100,000 a month, neither of them requires spousal or childcare support.