In December 2014, John Rust wrote to the head of the legal department at the University of Cambridge, where he is a professor, warning them that a storm was brewing.

According to an email reviewed by WIRED, Rust informed the university that one of the school’s psychology professors, Aleksandr Kogan, was using an app he created to collect data on millions of Facebook users without their knowledge. Not only did the app collect data on people who opted into it, it also collected data on those users’ Facebook friends. He wrote that if just 100,000 people opted into the app, and if they had an average of 150 friends each, Kogan would have access to 15 million people’s data, which he could then use for the purposes of political persuasion. Journalists had already begun poking around, and Rust wanted the school to intervene, arguing Kogan’s work put the university at risk of “considerable media attention, almost entirely adverse.”

“Their intention is to extend this to the entire US population and use it within an election campaign,” Rust wrote of Kogan and his client, a little-known political consulting firm that went on to be called Cambridge Analytica. He predicted, “I simply can’t see this one going away.”

Six months later, Donald Trump announced his candidacy for President of the United States, and launched a campaign that depended, in part, on Cambridge Analytica's work. His shocking election victory in 2016 thrust the firm into the spotlight, earning the company contracts with major commercial clients around the world. But more than a year after it helped get Trump in the White House, news broke that Cambridge Analytica had hired Kogan to harvest the data of tens of millions of American Facebook users without their consent, stoking international outrage from those who felt their privacy had been violated.

As director of the university’s Psychometrics Centre, which researches and develops psychological tests, Rust knew better than most how Facebook data can be manipulated. It was researchers in his own lab who first discovered that Facebook likes could be used to deduce all sorts of sensitive information about people’s personalities and political persuasions. But he says the goal of that research—and the goal of his 40 years in the field—was to warn the world about what can be done with this data and the dangers of allowing it to be so freely traded.

Years later, Rust takes no joy in being proven right. “We could see even four years ago the potential damage it would do, and there was nothing we seemed to be able to do to stop it,” he says today.

Facebook now acknowledges that Kogan collected the Facebook data of up to 87 million Americans and sold it to Cambridge Analytica. But as CEO Mark Zuckerberg and his team attempt to clean up the mess, Rust is hardly being hailed as some digital Paul Revere. Instead, his entire department and indeed his entire legacy have been swept up with both Kogan and Cambridge Analytica, accused by Zuckerberg himself of committing the very violations that Rust tried to warn against. “Our number one goal is to protect people’s data first and foremost,” says Ime Archibong, Facebook’s director of product partnerships. “We have an opportunity to do better.”

Since this spring, when news of the scandal broke, Facebook has cut off several apps used in the Psychometrics Centre's work, and in his testimony before Congress earlier this year, Zuckerberg suggested that “something bad” might be going on within the department that required further investigation from Facebook. In written responses submitted to Congress last week, Facebook mentions the Psychometrics Centre 16 times, always in conjunction with Kogan, who briefly collaborated with the researchers there.