THEIR marriage was anything but ordinary. Their divorce has been extraordinary.

He is a Russian billionaire worth $11.8 billion, and she is the thorn in his side expected to take half of his money in a drawn-out divorce labelled the “costliest breakup of all time”.

Dmitry and Elena Rybolovleva were college sweethearts. They met on their first day of university in the Russian city of Perm. His stock rose quickly. Very quickly.

Before long, he was one of Russia’s — and the world’s — richest men, a wealth acquired via the doctor-turned-entrepreneur’s booming fertiliser business.

She was there for the good times and there for the bad times, including the 11 months her husband was in jail. He was accused of murder but the charges were later dropped.

The love story included two children, mansions around the world, Central Park apartments and Swiss ski chalets. It was the best that money and love could buy, but it all began to unravel in the mid-2000s.

Lessons from the World's Most Expensive Divorce Russian oligarch Dmitry Rybolovlev has been ordered to pay his wife roughly $4.5 billion dollars in what is being billed as the world's most expensive divorce settlement. Are there lessons here for couples at all income levels? Financial planner Eleanor Blayney discusses. Photo: Getty

On New Year’s Eve in 2008, Elena filed for divorce. Forbes said she was tired of her husband’s infidelities. Court documents suggested the billionaire often threw lavish yacht parties where he “shared young conquests with his friends, and other oligarchs.”

It was always going to be messy, but nobody could’ve predicted just how messy it would become.

In May, 2014, a Swiss court awarded Elena over four billion Swiss francs ($5.7 billion) — the equivalent of around half her ex-husband’s entire fortune — as part of their split.

Mr Rybolovlev, the 49-year-old owner of French football club AS Monaco, is said to be the 154th richest man in the world. He first made his fortune selling fertiliser.

The pair said in a joint statement this week they had “reached an agreement on the terms of the divorce” in a move they said “puts an end to all legal procedures launched in different jurisdictions.”.

The statement did not specify the amount agreed upon.

The agreement came after a Geneva appeals court in June overturned the 2014 ruling, downgrading the payment required from Mr Rybolovlev to 564 million Swiss francs ($802 million), along with two real estate holdings.

One of the contentious points was Mr Rybolovlev’s worth, as he had transferred shares in 2005 to a trust and then sold them three years later at a huge profit.

His ex-wife’s lawyers argued that the appeals court calculated his net worth on the basis of the 2005 figures and not the 2008 ones.

They appealed the June ruling to the country’s highest court, but following the agreement announced Tuesday, the court will no longer be called upon to rule in the case.

The couple married in Cyprus and were together for 23 years, but have been battling over the terms of their divorce since 2008.

Dmitry Rybolovlev has recently made headlines over his conflict with a Swiss art dealer, Yves Bouvier.

The Russian tycoon, a big collector of art, has accused Bouvier of selling him works by the likes of Picasso, Modigliani, Degas and Gauguin at hugely inflated prices.