In 1995, the internet was a world of dial-up connections and Usenet newsgroups, but according to his biographer, Terry Pratchett had already “accurately predicted how the internet would propagate and legitimise fake news”.

Marc Burrows was digging through old cuttings about the late Discworld author for his forthcoming biography when he came across an interview Pratchett had done with Microsoft founder Bill Gates in July 1995, for GQ. “Let’s say I call myself the Institute for Something-or-other and I decide to promote a spurious treatise saying the Jews were entirely responsible for the second world war and the Holocaust didn’t happen,” said Pratchett, almost 25 years ago. “And it goes out there on the internet and is available on the same terms as any piece of historical research which has undergone peer review and so on. There’s a kind of parity of esteem of information on the net. It’s all there: there’s no way of finding out whether this stuff has any bottom to it or whether someone has just made it up.”

Gates, as Burrows points out, didn’t believe him, telling Pratchett that “electronics gives us a way of classifying things”, and “you will have authorities on the net and because an article is contained in their index it will mean something … The whole way that you can check somebody’s reputation will be so much more sophisticated on the net than it is in print,” predicted Gates, who goes on to redeem himself in the interview by also predicting DVDs and online video streaming.

Burrows’ unauthorised biography of Pratchett is out next August from Pen & Sword. The author, who is interviewing dozens of Pratchett’s contemporaries and colleagues for the book, said it wasn’t a huge surprise that his subject was so prescient as he had been a journalist and a press officer before he became a full-time writer.

Burrows said: “He’s someone who understood how a story worked and how robustly facts need to be checked, and as a press officer he would have known how quickly misinformation spreads. It comes up quite a lot in his work, most obviously in The Truth. He makes good use of the old saying about how ‘a lie can make its way around the world before the truth has got its boots on’ (often misattributed to him as a result), and invents a tabloid press to prove his point.

“Pratchett was someone who really understood human nature. Gates is an optimist, and an idealist – Pratchett was a realist, if not necessarily a cynic. He was absolutely bang-on.”

Pratchett, who sold more than 75m copies of his many novels, started his career as a reporter for the Bucks Free Press at the age of 17. His Discworld novel The Truth is a blistering satire on the press, as William de Worde launches Ankh-Morpork’s first daily newspaper. “The rumour spread through the city like wildfire (which had quite often spread through Ankh-Morpork since its citizens had learned the words ‘fire insurance’). The dwarfs can turn lead into gold,” writes Pratchett as the novel opens. “And the rumour came to the ears of William de Worde, and in a sense it stopped there, because he dutifully wrote it down.”

Burrows’ original tweet about the GQ interview went viral this week. He told the Guardian that, ironically, “hardly anyone has asked if a quote about the dangers of spreading fake news on the internet is actually real”.

“It’s literally just a photo from an article in an old magazine, I could easily have faked it,” he said. “Everyone’s taken my word for it. It is real, but I thought that was really interesting. Here’s Terry saying ‘don’t take everything online at face value’, and literally thousands of people respond by going ‘Terry is so clever’ and hitting RT. I think he’d appreciate that.”