When Eva Rausing approached the heavily guarded U.S. Embassy in London's Grosvenor Square four years ago to deal with a routine passport matter, she had to pass through British security, then face an airport-style metal detector so she and her handbag could be scanned for weapons and contraband.

The wealthy American didn't leave her stash at home. She tried to pass the security scan with small amounts of crack cocaine, heroin and a banned stimulant in her purse.

The subsequent arrest led police to search the multimillion-dollar property she shared with her husband, Tetra Pak heir Hans Kristian Rausing, 49. Police found still more drugs, including a sizable amount of cocaine.

Hans Kristian Rausing and Eva Rausing met at a rehabilitation clinic in the United States 25 years ago. (Alan Davidson/The Picture Library/Associated Press)

Charges were dropped in exchange for a formal police warning, but the arrest made public what close family and friends already knew: The golden couple, with untold riches, were deeply mired in drug addiction even as they gave millions to numerous anti-addiction charities.

Their sad tale reached its climax this week when the 48-year-old Eva Rausing was found dead in their home and her husband arrested for questioning about drug use and placed in hospital care. The cause of Eva Rausing's death has not yet been established. Investigators are examining whether she may have been dead for a week before the discovery of her body, according to the Guardian newspaper.

Drugs are a scourge for the poor, for the middle class and even for the super-rich, those who, like the Rausings, measure their net worth in the billions.

"Addiction doesn't know any class boundaries," said Amanda Thomson, spokeswoman for Action on Addiction, one of many charities the Rausings supported even as they swooned toward drugged-out oblivion.

Family on 'Rich List'

Eva Rausing was born into a wealthy American family headed by former Pepsi executive Tom Kemeny, and her husband was an heir to the formidable Tetra Pak fortune — his father and his family have a spot on Britain's "Rich List" with a net worth estimated at £4.3 billion ($6.7 billion).

The money came from his family's development of a better milk carton — one that could be packed and shipped like bricks, easing the distribution of milk and juices throughout the world.

The Rausings married shortly after they met at a rehabilitation clinic in the U.S. 25 years ago and raised four children — aged 11 to 17 — from their London base in an exclusive section of the Chelsea neighbourhood.

Before the embassy arrest, Eva Rausing's good looks and beautiful clothes — along with her husband and his friendly, bear-like countenance — had made the Rausings welcome participants on the London philanthropic scene. She was on several charity boards, focusing on those that helped fight drug addiction, but also serving on Prince Charles's Foundation for the Built Environment.

Charles, no stranger to second chances, stood behind her after the embassy scandal, backing a decision to keep her on board as a trustee. A spokeswoman, who declined to be identified because of palace policy, said Charles, who was able to rebuild his life after his failed marriage to Diana, believes people can recover from serious missteps.

But evidence suggests that Eva Rausing's drug use only intensified in the years since the embassy arrest. Recent photographs show she had become quite gaunt, and her once stocky husband also recently appeared thin and furtive, bearing only a slight resemblance to his former self, when he would attend galas looking like an elegant, bearded, tuxedoed European swain from an earlier era.

Husband receiving medical treatment

Hans Kristian Rausing was arrested in connection to suspected drug crimes and police want to question him about the circumstances of his wife's death. He is currently receiving medical treatment in a London hospital. Police have not indicated that Eva Rausing's death was a result of foul play or that a crime was committed.

Liz Brewer, a friend of Eva Rausing, told Sky News that Rausing's problem had been "pushed under the carpet" for too long.

"She was totally addicted, obviously, and was trying to get off it," she said.

It has become common for celebrities like Elton John and Eric Clapton to use their fundraising power to help anti-addiction charities after they get off drugs, but experts say it is not unusual for people like the Rausings to work hard to help anti-addiction groups even as they struggle, sometimes unsuccessfully, to get clean.

In Eva Rausing's case, she served as a trustee of the anti-addiction charities Chemical Dependency Center and Clouds beginning in the late 1990s, long before her embassy arrest. Those organizations merged with Action on Addiction, a charity supported by Eva Rausing until her death that also has a strong link to the royal family: the former Kate Middleton is a patron.

CEO Neil Barton said that over the years, the Rausings contributed tens of millions of pounds to the anti-addiction crusade, remaining committed even after Eva Rausing stepped down as a trustee. He said he never discussed Rausing's addiction with her.

"I didn't want to go there unless she wanted to talk about it," he said, describing Rausing as a charming woman with an easy smile. "I don't remember ever having that sort of conversation with her, but it was understood that that was partly why she was interested."

Eva Rausing's parents issued a statement paying tribute to a "devoted wife" and mother of "much loved and wonderful children" saying they were devastated over her death. Their statement also alluded to her struggles with addiction.

"During her short lifetime she made a huge philanthropic impact, supporting a large number of charitable causes, not only financially, but using her own personal experiences," the family said. "She bravely fought her health issues for many years."