They are the British-Iranian clan behind the “world’s largest bribe scandal”.

Cyrus Ahsani, his brother Saman Ahsani, and their 17-year-old son worked as fixers for multinationals like Rolls-Royce. They bribed officials in Algeria and Angola, Azerbaijan and the Democratic Republic of the Congo.

The Guardian now has leaked documents showing how the proceeds from Unaoil’s family firm were laundered through a complex chain of offshore companies, which secretly funded the purchase of several UK properties.

The Pandora papers are a massive leak of confidential offshore records that the International Consortium of Investigative Journalismists shared with Guardian and other media partners around world. It contains a cache of documents which appears to show how approximately PS7.5m of Unaoil profits were funneled via offshore companies into investment fund and blended with funds from outside investors.

This money was apparently then invested at the recommendation of another Ahsani company in London to purchase seemingly ordinary – and often unscrutinised- assets such as a multiplex cinema, Humberside business park, and Slough office block.

According to an analysis by the Guardian of public documents, the portfolio had a value of more than PS200m.

These revelations, which reveal that millions of British pounds worth of real estate was tainted with money made at one of the most notorious corporate bribery scandals in history, will only increase existing concerns that the UK’s housing market is being used to hide corrupt state fortunes by white-collar criminals or kleptocrats.

The Home Office and Treasury stated that the money laundering risk in the UK’s property sector has increased from medium-high to high since 2017. They warned: “Commercial real estate, especially office space, remains attractive to money launderers.”

These disclosures will likely raise concerns for the Serious Fraud Office. Even though Ahsanis was the subject of one of its most prominent criminal investigations, the agency has yet to take legal action against Ahsanis for the confiscation of the Ahsanis’ money.

Five years ago, Fairfax Media in Australia exposed Unaoil’s corrupt schemes. They called it the “world’s largest bribe scandal”. They discovered that multinational companies had used Unaoil (the Ahsanis’ Monaco-based company) for years to pay bribes in order to secure large contracts in Africa, Asia and the Middle East.

Both Cyrus and Saman Ahsani were found guilty of facilitating the payment of bribes between 1996 and 2016 to officials from Africa and the Middle East. They also admitted to laundering money to hide the bribes.

They will be sentenced by a Texas court in December. Three multinationals also paid US penalties for their participation in the bribery.

The SFO successfully prosecuted four Unaoil employees in the UK courts. They have been sentenced.

Anti-corruption activists are asking why Ata Ahsani (81-year-old family head) has not been charged or prosecuted in any country. They also point out that while the SFO has charged junior Unaoil employees, it did not prosecute the family patriarch who was the founder of Unaoil.

Ata Ahsani, a US citizen, has agreed with the US Department of Justice to not face prosecution. Although the terms of the agreement are not known, lawyers representing the Ahsanis don’t dispute it.

Between 2016 and 2018, Tom Martin was the SFO’s lead investigator into Unaoil. A tribunal of employment ruled that Martin was unfairly fired by the SFO. The tribunal heard that Ata Ahsani had agreed to a deal with DoJ in which he would pay $2m (PS1.47m), to the US authorities.

Jim Sturman was a barrister representing one of the junior Unaoil workers who was convicted for corruption. He claimed in court that “remarkably Ata Ahsani appears to have been allowed by the US authorities to get out of any prosecution through a financial payment to them as an alternative to prosecution”.

Ata Ahsani’s lawyers claimed it was fanciful to suggest that one could (simply) pay any amount of money to obtain a non-prosecution arrangement.

Martin, who was also at the tribunal, stated that the Ahsanis had amassed $200m through Unaoil’s corrupt schemes and had once wanted to make a deal for the sake of not losing this fortune.

Lawyers representing the Ahsanis claimed that this number was incorrect and an exaggerated assertion made by Martin, who has never been able substantiate it. They also stated that the UK’s criminal law does not permit the cutting of deals. They stated that it was incorrect to suggest that Unaoil’s entire business was illegal. They also said that US and UK prosecutors had not found that Unaoil had derived all its profits from bribery.

Spotlight on Corruption’s executive director Susan Hawley said that junior employees are being punished for their corrupt behavior. The person running the company, who is most likely to have benefited from Unaoil’s corrupt behaviour, gets to walk off with a minor fine. This sends a disturbing message to senior executives that they are not a priority in prosecutors, which severely undermines the fight against corrupt practices.

Documents now reveal for the first-time how Unaoil proceeds were invested by the Ahsani family.

BBC File on Four and the Guardian jointly investigated documents that were leaked by an offshore service provider. The documents showed that Ata Ahsani invested the money in two property funds called Lumina Real Estate Capital special situations funds.

Also, the papers show that Ata’s source of investment was “earnings from Mr [Ata] Ahsani – Unaoil Group”.

According to leaked records, a fourth BVI company was formed in 2005 and is listed as having been funded by “earnings from Mr Ahsani Saman by Unaoil Group”.

Ata Ahsani, who is beneficially the owner of a fifth BVI company but was not linked to Lumina according to leaked papers, reported that it holds EUR6.5m (PS5.6m), of “office space” assets. These were once again identified as funds from Unaoil Group’s “earnings Mr Ahsani”.

Lawyers for Ahsanis claimed that Ata Ahsani only financed 5% of the two Lumina Funds.

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