Troubled heir to the £5bn Tetra Pak fortune

Crack cocaine, the drug of the backstreets, is not something one would normally associate with Hans Kristian Rausing and his American heiress wife.

This couple, both 44, live in a world of wealth and privilege as far removed as it is possible to imagine from crack's traditional image of smoking dens and street corners haunted by the sad victims of the drug and its malignant influence.

Yet news that Hans Kristian and his wife Eva have been arrested on suspicion of possessing both crack cocaine and heroin will not shock everyone. To the outside world they appear to lead a gilded existence, surrounded by the luxury and attention that can be bought from a share in a £5.4billion fortune. But those who know them speak quietly of people who have fought hard - and not always successfully - against addictions they picked up in their youth. Indeed, Hans Kristian and Eva met while attending a rehab clinic in America.

Friends of the couple say they have fought drug problems for years, secretly and with quiet determination. Now their secret is out.

It also shows how crack has risen out of the inner-city ghettoes and been adopted by some middle-class drug users.

The couple's arrest won't change their standing in the eyes of those who have benefited from the Rausings' generosity towards others whose lives have been damaged by drugs. While the family patriarch, Dr Hans Rausing and his two daughters, Lisbet and Sigrid are busily adding to the family wealth at a rate of nearly £10 million a week, Hans K, as he is known in the family, is more likely to be found working with young people who have also known the horrors of drugs.

Hans K uses money from an inherited trust to fund a number of charities, prompting Prince Charles, with whom he is on first-name terms, to call him "one very special philanthropist".

The cause that is closest to Hans K's heart is Mentor, a charity that runs projects in Britain and abroad to keep young people away from drugs. It operates in schools, universities and communities and claims to have helped more than a million children in 40 countries in the past 10 years.

Eva Rausing is a patron of the charity and she and her husband regularly attend its functions, including a gala dinner at the Natural History Museum which they helped pay for. The couple also run their own charitable trust, and give away millions every year.

They live in a five-storey house off Cadogan Square in Chelsea - the house raided by police after Mrs Rausing was found trying to enter a party at the American embassy allegedly with drugs in her handbag - and they are surrounded by the usual trappings of wealth, including servants and expensive cars.

She is a keen tennis player and takes a generous interest in the Mary Rose Trust, established to save Henry VIII's salvaged battleship. The couple have also given large amounts to the Royal Opera House, which they attend often.

But they are not socialites in the usually accepted sense. One person who knows them said: "It is very difficult to have a conversation with him. He has a detached, non-communicative manner. I asked him what his interests were and he said, after a long pause, opera. 'What have you seen recently?' I asked. He seemed stumped, then turned to his wife and asked her. Neither could remember."

Unlike Hans K, his sisters Lisbet and Sigrid have taken an active role in increasing the Rausing billions. The fortune began with their grandfather Ruben, a Swedish inventor who created the waxed paper carton that was the foundation of the Tetra Pak (later Tetra Laval) packaging empire.

Ruben's son, Hans, took over the firm with his brother and ran it from Lund, in southern Sweden, where Hans Kristian and his sisters grew up.

Lisbet, married to historian Peter Baldwin, with whom she has two children, lives in Holland Park. She also has a 48,000-acre estate near Fort William in Scotland. Sigrid, the middle child, is married to filmmaker Eric Abraham. They also live in Holland Park, in a house said to have the biggest private garden in London after Buckingham Palace. Sigrid also owns a 40,000-acre estate in Scotland, near Inverness. The family's money has been invested in a wide range of other businesses controlled through family trusts, some registered in the Cayman Islands and therefore virtually impenetrable.

Philip Beresford, compiler of the Rich List, said: "Dr Rausing is still incredibly sharp and, in a low-key way, still making lots of money. The wealth is percolating down to his children now and they are controlling more of it."

It is not known how each of the Rausing children benefits individually from the way the family's money is arranged, but while Hans K does not appear to own vast estates like his sisters, he lives extremely comfortably.

He used to live in a house on Cadogan Square which, when offered for sale at £14 million in 2006, was one of London's most expensive homes. It was eventually sold for £12.65 million and Hans K, Eva and their four children moved into an equally impressive house around the corner in Cadogan Place. Eva is the daughter of American businessman Tom Kemeny, who lives on an island off the coast of South Carolina.

The Kemenys also have a house on Barbados and were there to celebrate the millennium with their other daughter, Be. Hans Kristian and Eva recently finished building one of the biggest homes on Barbados, a house in a vast compound behind high walls in parklike grounds and with staff quarters, on the site of an old hotel near Sandy Lane. It is said to have cost £15 million.

The family party for the millennium was also attended by Jack Kidd, the polo-playing brother of model Jodie Kidd. Kidd and Be hit it off, it seemed, and were married later that year in London. They had four children, but split after five years when Be, who had used part of her estimated £30 million fortune to buy Kidd a £2 million polo farm, discovered there were other women in his life.

She shared this with about 200 friends by emailing them from Kidd's computer saying their marriage was over. Then she smashed the computer and flew back to South Carolina with her children.

Sigrid Rausing has also known the upset of a marriage break-up. Her first husband was South African publisher and art dealer Dennis Hotz. After their divorce she married Mr Abraham, a former producer on the BBC's Panorama.

The couple run an independent publishing and film company, Portobello. When Sigrid bought Aubrey House in Holland Park in 1997, for £20 million, it was then said to be London's most expensive home. But she spends an increasing amount of time at her estate in the Monadhliath mountains.

Scotland, she said, gives her a feel of the wilderness she knew as a child in Sweden. Which might prompt some to ask - why do the Rausings choose to live here? The answer, of course, is tax.

Dr Rausing is non-domiciled for tax purposes and an analysis of his affairs, published five years ago, revealed clever, but entirely legitimate, tax avoidance. This analysis claimed that while Dr Rausing does pay tax on part of his income, he manages to save millions by being non-domiciled.

Dr Rausing is said to be almost comically careful about money in some ways - he uses an old Morris Minor and has his hair cut by the village barber - but it is estimated he and his family have given away more than £140 million.

And Hans K and Eva have given untold amounts to their drug charities. Whether their work with addicts will continue following their current difficulties with the police remains to be seen.