The Fujitsu U.K. Post Office scandal, explained

For weeks, the U.K. has been gripped by the Post Office Horizon scandal. And now, as the rest of the world begins to pay attention to the odd incident caused by a tech glitch, more people are asking: What the hell is going on?

Here’s a quick guide to this wild, and ongoing, saga.

What went wrong at the Post Office?

Between 1999 and 2015, glitches in accounting software used by the U.K. Post Office meant that large amounts of money appeared to go missing from more than 700 post offices. Post Office Limited, the private company that runs the state-owned service, began pursuing sub-postmasters and mistresses, the men and women that oversaw Post Office outlets, for compensation for the missing money.

More than 700 people were convicted over the course of 16 years for the accounting discrepancies, which the Post Office claimed was theft. But a U.K. High Court judgment in 2019 found that individual sub-postmasters and mistresses weren’t to blame for the figures not adding up: The culprit was in fact the accounting software, called Horizon, that sub-postmasters and mistresses were required to use to calculate their profits and losses at each branch. Trade magazine Computer Weekly found that a glitch in Horizon froze the screen when an operator tried inputting money, meaning every time someone clicked on it subsequently it repeated the transaction. They also found a bug that duplicated entries without any human input. These were just some of the many issues discovered.

A public inquiry, commissioned in the wake of the 2019 High Court decision, is currently ongoing—and the scandal has received renewed public interest thanks in part to a new TV drama called Mr Bates vs The Post Office, which tells the story of those who were alleged to have done wrong and campaigned to clear their name. Outrage remains because to date fewer than 100 of those more than 700 convicted have seen their judgments overturned.

The U.K. government has set aside $1.27 billion for potential payouts to those affected. The root cause of the issue—which is likely to cost the Post Office millions in compensation payments, and could cost Fujitsu, the makers of the Horizon software, many lucrative government contracts—was simple. And it’s one that could happen anywhere, not just the U.K.

It was an unflappable faith in the infallibility of software, and an unwillingness to accept the more rational explanation—that something had gone wrong, rather than 700 or more people across the country who had previously shown no signs of criminality had simultaneously decided to defraud a company in the exact same way. “There’s this kind of default position that technology is kind of perfect,” says Catherine Flick, a professor of ethics and technology at Staffordshire University. “And that it’s not going to do anything outside of the envisioned boundaries of its operation.” But that overlooks the existence of bugs in software, and the fact that they’re coded by humans who can make mistakes.

Such a belief is enshrined in law. “A little-known detail of the Post Office scandal is that, due to some astoundingly bad decisions made in the 1990s, English law presumes that computer evidence is reliable,” says Dan McQuillan, a lecturer in creative and social computing at Goldsmiths, University of London.

Why is this whole thing so scandalous?

Even after the Post Office executives knew that the software system was at fault as early as 2013, when it was raised by an independent team of forensic accountants brought in to investigate why the money kept going missing, the company allegedly sought to keep that information quiet. The BBC reports that the company fired the accountancy team finding the issues.

The notion that computers can’t possibly be wrong—despite overwhelming evidence to the contrary—remains strong among those who were involved in investigating the missing money within the Post Office. Just this week, one investigator who prosecuted a postmaster who has since died, but whose prosecution was quashed posthumously, said he still believed the man was guilty. The investigator, Raymond Grant, had to be legally compelled to appear at the inquiry, and said he had been too busy making Christmas meals and walking his dog to adequately prepare for his appearance at the inquiry.

The inquiry continues, while the Post Office and Fujitsu have apologized in front of the inquiry. Paul Patterson, Fujitsu’s European chief, told the inquiry last week that “This is a decades-old miscarriage.” He added: “I think Fujitsu more recently, as we’ve understood more, we have clearly let society down and the sub-postmasters down.”

For weeks, the U.K. has been gripped by the Post Office Horizon scandal. And now, as the rest of the world begins to pay attention to the odd incident caused by a tech glitch, more people are asking: What the hell is going on?

Here’s a quick guide to this wild, and ongoing, saga.

What went wrong at the Post Office?

Between 1999 and 2015, glitches in accounting software used by the U.K. Post Office meant that large amounts of money appeared to go missing from more than 700 post offices. Post Office Limited, the private company that runs the state-owned service, began pursuing sub-postmasters and mistresses, the men and women that oversaw Post Office outlets, for compensation for the missing money.

More than 700 people were convicted over the course of 16 years for the accounting discrepancies, which the Post Office claimed was theft. But a U.K. High Court judgment in 2019 found that individual sub-postmasters and mistresses weren’t to blame for the figures not adding up: The culprit was in fact the accounting software, called Horizon, that sub-postmasters and mistresses were required to use to calculate their profits and losses at each branch. Trade magazine Computer Weekly found that a glitch in Horizon froze the screen when an operator tried inputting money, meaning every time someone clicked on it subsequently it repeated the transaction. They also found a bug that duplicated entries without any human input. These were just some of the many issues discovered.

A public inquiry, commissioned in the wake of the 2019 High Court decision, is currently ongoing—and the scandal has received renewed public interest thanks in part to a new TV drama called Mr Bates vs The Post Office, which tells the story of those who were alleged to have done wrong and campaigned to clear their name. Outrage remains because to date fewer than 100 of those more than 700 convicted have seen their judgments overturned.

The U.K. government has set aside $1.27 billion for potential payouts to those affected. The root cause of the issue—which is likely to cost the Post Office millions in compensation payments, and could cost Fujitsu, the makers of the Horizon software, many lucrative government contracts—was simple. And it’s one that could happen anywhere, not just the U.K.

It was an unflappable faith in the infallibility of software, and an unwillingness to accept the more rational explanation—that something had gone wrong, rather than 700 or more people across the country who had previously shown no signs of criminality had simultaneously decided to defraud a company in the exact same way. “There’s this kind of default position that technology is kind of perfect,” says Catherine Flick, a professor of ethics and technology at Staffordshire University. “And that it’s not going to do anything outside of the envisioned boundaries of its operation.” But that overlooks the existence of bugs in software, and the fact that they’re coded by humans who can make mistakes.

Such a belief is enshrined in law. “A little-known detail of the Post Office scandal is that, due to some astoundingly bad decisions made in the 1990s, English law presumes that computer evidence is reliable,” says Dan McQuillan, a lecturer in creative and social computing at Goldsmiths, University of London.

Why is this whole thing so scandalous?

Even after the Post Office executives knew that the software system was at fault as early as 2013, when it was raised by an independent team of forensic accountants brought in to investigate why the money kept going missing, the company allegedly sought to keep that information quiet. The BBC reports that the company fired the accountancy team finding the issues.

The notion that computers can’t possibly be wrong—despite overwhelming evidence to the contrary—remains strong among those who were involved in investigating the missing money within the Post Office. Just this week, one investigator who prosecuted a postmaster who has since died, but whose prosecution was quashed posthumously, said he still believed the man was guilty. The investigator, Raymond Grant, had to be legally compelled to appear at the inquiry, and said he had been too busy making Christmas meals and walking his dog to adequately prepare for his appearance at the inquiry.

The inquiry continues, while the Post Office and Fujitsu have apologized in front of the inquiry. Paul Patterson, Fujitsu’s European chief, told the inquiry last week that “This is a decades-old miscarriage.” He added: “I think Fujitsu more recently, as we’ve understood more, we have clearly let society down and the sub-postmasters down.”