In the largest exposé on the financial system since 2016’s Panama Papers leak, Buzzfeed News has obtained over 2,500 documents revealing the extent of corruption in the global banking system. Known as the ‘FinCEN Files’, the 2,657 documents include 2,121 suspicious activity reports, which banks send to authorities in order to raise concerns about just where some of their clients’ money might be coming from.

FinCEN is the US Financial Crimes Enforcement Network, a department of the US Treasury responsible for combating any financial crime involving US dollars, wherever it takes place the world. Should a bank be worried that one of its clients isn’t legitimate, or is engaged in illegal activities, it should send a suspicious activity report (SARs) to FinCEN.

The leaked files, which span the period between 2000 and 2017, cover roughly $2 trillion of transactions and are said to reveal how some of the world’s largest banks have enabled criminal enterprises to launder dirty money.

Usually these documents are a closely guarded secret, but a batch was leaked to Buzzfeed News who shared them with the International Consortium of Investigative Journalists (ICIJ), which in turn shared them with over 108 news organisations in 88 countries. Speaking to the BBC, Fergus Shiel from ICIJ explained that the leaked files were an “insight into what banks know about the vast flows of dirty money across the globe”.

And, while the transactions may be in USD, the UK has a special role to play in the story. According to FinCEN the UK is a “higher risk jurisdiction” due to the overwhelming number of UK companies named in the files – over 3,000.

Some of the revelations that have come to light include Chelsea owner Roman Abramovich’s previous ownership of secret investments in non-Chelsea footballers through an offshore company; JP Morgan allowing an unknown company whose owners may or may not be on the FBI’s Most Wanted list to move more than $1bn through a London account; and that the husband of a woman who has donated £1.7m to the Conservative Party was secretly funded by a Russian oligarch with ties to President Putin.

“Giants of Western banking move trillions of dollars in suspicious transactions, enriching themselves and their shareholders while facilitating the work of terrorists, kleptocrats, and drug kingpins,” write the 11 authors of the Buzzfeed exposé. “Profits from deadly drug wars, fortunes embezzled from developing countries, and hard-earned savings stolen in a Ponzi scheme were all allowed to flow into and out of these financial institutions, despite warnings from the banks’ own employees.”

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Far from being a harmless, victimless crime, money laundering is serious business. “It is the very fuel of crime,” Martin Woods, former money laundering reporting officer told the BBC. “If we continue to launder money, criminals will continue to commit the crimes, to kill people over drugs, to supply drugs that kill people in our community…Banks or bankers for too long have seen it in the abstract and removed it from the crime. We need to join those dots up again.”