From the terrace of the Miami Beach club, the sand stretches down to the Atlantic ocean. Waves lap the long shoreline of the Ilha de Luanda. On weekends, the bar-restaurant is full of wealthy drinkers and dancers who have driven over from Luanda, the Angolan capital, a few kilometres away.

The Miami Beach club has been a fixture on the Luanda party scene for 20 years. Over that time the civil war that devastated Angola ended, an oil boom that generated billions ended in bust, and one of the longest-ruling leaders in Africa, José Eduardo dos Santos, was forced to step down as president. It was a period when a lucky elite of Angolans made very large fortunes – but none seems to have made more than the former president’s daughter, Isabel dos Santos, whom Forbes says is worth $2.2bn (£1.7bn).

The beach bar was Dos Santos’s first foray into business in Angola, and it marked her out as a savvy investor. In her mid-20s, having recently returned to Angola after studying in London, Dos Santos acquired a stake in what was then a struggling, scruffy bar. The money was wisely spent. The Ilha is now one of the most fashionable and valuable locations on the entire western coast of Africa between Cape Town and Lagos. One person who has not been seen on the premises in a long time, however, is Dos Santos, now the richest woman in Africa.

Q&A What is the Luanda Leaks investigation? Show Hide The Luanda Leaks project is based on a trove of 715,000 emails, charts, contracts, audits and accounts detailing the business operations of Isabel dos Santos, the daughter of the former president of Angola. The files were initially obtained by the anti-corruption charity Platform to Protect Whistleblowers in Africa (PPLAAF), which shared them with the International Consortium of Investigative Journalists (ICIJ). The documents, which cover a period between 1980 and 2018, have been reviewed by more than 120 journalists from 37 media outlets, including the Guardian, the BBC and the Portuguese newspaper Expresso.

Critics allege her vast fortune is an outrage in one of the world’s poorest countries, a flagrant example, they claim, of a brand of nepotistic corruption that scars so many African nations. Dos Santos, 46, insists her wealth is the result of hard work and business acumen, and her supporters say her success story is inspirational, especially for African women.

Precisely how Dos Santos made so much money is the subject of mounting scrutiny. Angolan prosecutors launched a criminal investigation into her actions while at the helm of the state oil company, Sonangol, in September. Three weeks ago, in a separate move, the country’s attorney general announced a freeze on the assets of Dos Santos and her husband, Sindika Dokolo, claiming their dealings with the country’s publicly owned oil and diamond companies had “harmed” the state to the tune of $1bn.

Facebook Twitter Pinterest Isabel dos Santos (left) with her husband, Sindika Dokolo, in Cannes in 2018. Photograph: Dave Benett/amfAR

The couple have fiercely denied any wrongdoing in a series of public interviews that appear to have been timed to get ahead of this week’s reports from 37 media outlets, including the Guardian, which have had access to a leaked cache of financial records from Isabel dos Santos’s business empire.

Dos Santos was born in 1973 in Baku, Azerbaijan, where her parents had met. Her father was then an official in the Communist-aligned Popular Movement for the Liberation of Angola (MPLA) and had been sent to study engineering in the USSR. Her mother was a chess champion, who was studying the same subject. Two years later, the Portuguese colonial regime collapsed and four years after that, in 1979, José Eduardo dos Santos took over the leadership of the fledgling free nation and the family moved into the presidential palace.

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After her parents divorced and the country plunged into a civil war, Isabel Dos Santos went with her mother to London to be educated at St Paul’s girls school. She left with A-levels in maths, further maths and physics, and took a bachelor’s degree in electrical engineering at King’s College London, where she worked hard, she later told interviewers, and had little time for partying. After graduating, she spent two years at Coopers & Lybrand, the accountancy firm now known as PwC.

Later, when it briefly looked like the civil war was over, she returned to Angola, where she started a transport business. Dealing with communications for trucks led her to mobile phone technology, then in its infancy. This proved fortuitous, and she rejects absolutely any suggestion that being the eldest daughter of the president helped when a consortium she was part of won a public tender for a licence – only the second in Angola – for mobile telecommunications towards the end of the 1990s. Unitel is now the country’s biggest mobile phone provider.

From then on, her business empire has grown and grown, prompting further allegations, which she denies, that her father’s influence, direct or indirect, helped her to amass fabulous riches. She also owns large parts of Angola’s cement, diamond and banking industry, as well as stakes in a supermarket network, a satellite TV chain and a brewery.

Dos Santos says she is the subject of a politically motived “witch-hunt”, and denies the allegations of corruption and nepotism levelled against her. In a recent interview with the Economist, she said she founded Unitel in an office above a shop where she sold phones to market women, and claimed the success of her supermarkets was because they had “the best fish section in the country”. She told the Financial Times: “The press calls me princess. I don’t know many princesses who get out of bed and build supermarkets.”

Dos Santos was also lucky. Her entry into the small and secretive world of Angola’s business elite came at a time when the country was on the brink of a huge boom. Rising oil prices and rising production pushed revenue from about $3bn in 2002 to $70bn in 2008, though little trickled down to ordinary Angolans.

The country also received vast loans from China and elsewhere. Some of this money was spent on infrastructure, but the road and railway networks remain largely in ruins, and power generation is grossly inadequate. Drought has also caused massive hardship, with millions living in appalling conditions.

There were a lot of parties around Luanda as the cash rolled in. In 2012, Dos Santos threw a lavish bash, flying in dozens of friends to celebrate the 10th anniversary of her wedding to Dokolo, a Congolese businessman and art collector. The couple enjoy many of the trappings that would be unimaginable for most of Angola’s new middle class, let alone for those living in poverty.

Even in Luanda, millions live without adequate sanitation, housing or food and the World Bank has estimated two-thirds of the country’s population have to survive on less than $2 a day. Dokolo collects sports cars, and Instagram pictures show a superyacht, Hayken, bought from the London property developer Christian Candy.

Facebook Twitter Pinterest The superyacht Hayken. Photograph: VBH

A huge penthouse in Lisbon has parking space for seven cars. In London, the couple appear to own three homes in a single gated development in Kensington, including a large house with planning permission for an “iceberg” basement extension. There is also a luxury flat in the Petite Afrique building in Monte Carlo, bought for €50m through a Maltese holding company, and a sprawling villa in the Algarve.

Dokolo’s collection of African art, held by his foundation, is reputed to be the largest in the world, and he owns works by Andy Warhol and Jean-Michel Basquiat. The son of a Kinshasa banking tycoon, raised in Belgium and France, Dokolo acquired his first pieces at the age of 15.

Many recognise his wife as an effective manager. One businessman in Luanda called Dos Santos “ruthless and very sharp”. Others use less complimentary adjectives. The interests controlled by Dos Santos and her husband span two continents, after an investment spree in Portugal. There is an €800m slice of the oil and gas group Galp; a stake in the pay TV and broadband group Nos; a large shareholding in the Portuguese bank Eurobic, and stakes in banks in Angola and Cape Verde.

Facebook Twitter Pinterest Isabel dos Santos with Nicole Scherzinger, Chris Tucker and Mette Towley at a Cannes gala dinner in 2018. Photograph: Dave Benett/WireImage for amfAR

In 2016, Dos Santos was appointed chair of the state-owned oil company Sonangol, the beating heart of Angola’s oil industry, but was dismissed when João Lourenço, a senior MPLA official who replaced her father as president in 2017, launched an anti-corruption campaign. Dos Santos denies all allegations of wrongdoing made against her and says the investigations are politically motivated. Her lawyers describe the Angolan asset freeze as “nothing more than a politically motivated ‘witch-hunt’” by Lourenço.

Dos Santos is not the only member of her family under pressure. Her half-sister, Welwitschia dos Santos, was ousted as a member of parliament last year after fleeing to the UK, saying she was being harassed by the Angolan secret service; and her half-brother, José Filomeno dos Santos, is on trial for corruption. Both deny wrongdoing. Their father, the former president, is gravely ill in Barcelona.

“This is a political trial. You have a persecuting state and servile and partisan magistrates. Then you have a woman who has been chosen to set an example as a scapegoat. That’s me,” Isabel dos Santos told Reuters, speaking in London, which she has been claiming as her main residence.

Portuguese media reports suggest that may be about to change, amid suggestions she is relocating to a gated community in Dubai’s Jumeirah Bay.

One place Dos Santos is not expected to be seen any time soon is Angola. “I haven’t been to Angola since 2018,” she told a journalist last month. “Because today Angola is living in a situation of insecurity. Crime is very high, there are many robberies, there are many murders. It’s not a safe place.”