It's the year 1999. You've just taken the kids to see The Matrix. They're playing the recently-released Pokémon Red and Blue in the back seat. 'Genie in a Bottle' is playing on the radio. Again. In the morning, you're starting your new job as a sub-Postmaster at the Post Office.

With the rapid advances in technology all around you, imagine your disappointment when you show up in the morning and you're sat down in front of this beauty:

Those elegantly staggered tiles are one of the POS (Point-of-Sale) UIs for Horizon, an accounting and business package released by Fujitsu in 1999, and deployed to Post Office branches in the UK over the next several years starting in 2000.

Horizon, it turned out, was full of bugs. The kind of bugs you don't want in accounting software. As a result of a plethora of problems including poor number variable handling, poor error handling, a diabolical UI and an astonishing lack of updates, Horizon caused the UK Post Office to accuse over 3,500 staff of fraud, theft and false accounting.

Though the Post Office serves an almost-unique function in British society, it operates much like any other high-volume High Street cash business. That means if your till's short, you're short.

By 2015 the Post Office had secured over 700 criminal convictions of Post Office staff on the basis of discrepancies reported by Horizon.  

The errors in Horizon's software, logic and attitude towards support were exposed in a High Court ruling in 2019.

What was wrong with Horizon?

If the UI wasn't bad enough, here are some of Horizon's greatest hits:

• Randomly duplicating or deleting transactions
• Frequently popping up confusing error messages that were routinely dismissed as meaningless, but sometimes meant an error had been introduced into records
• Data entered into the system sometimes recorded incorrectly, rounded incorrectly, or stored as wrong variable type
• High volume of false positives in its fraud detection systems
• Lack of support or documentation for end users and managers

All of these together caused a constant stream of cashier shortfalls and discrepancies, which were always blamed on staff. If you've ever worked in a cash business like a restaurant, you can imagine who paid a lot of those shortfalls.

In fact, over 2,500 staff members were accused and forced to pay back the shortfall from their wages, or face prosecution.

At least it wasn't expensive?

The UK Post Office - a venerable public institution known for being perpetually short on cash - spent £1 Billion with a B implementing and maintaining this monstrosity, and more besides investigating and pressing charges against employees.

By the end of 2023 they'd spent another £138 million compensating victims of the scandal, with most cases still not settled.

That's terrible! And they only found out in 2019?

Of course not. 

The UK Post Office began to suspect issues with Horizon as early as a year after its implementation, in 2000. By 2010, they had discovered serious issues with its accounting outputs. But, they'd spent an awful lot of money on it, so they continued to prosecute sub-Postmasters and other staff for another five years, just in case.

It took a group of the defendants winning a High Court case in 2019 to force the post office to blame Horizon and begin to compensate victims

"At least there's a happy ending!"

Is what we'd say if a bunch of senior Post Office employees had been prosecuted for covering up a scandal and knowingly ruining a bunch of peoples' lives. But wouldn't you know it, they really want to but it's all just a bit complicated.

Paula Vennells, Post Office boss at the time, had to give back her CBE in 2024 to the sound of a teeny tiny violin, after someone told King Charles III it wasn't a good look.

Fewer than 150 cases had been looked at by the end of 2023, and of those nearly a third were upheld or refused permission to appeal.

Most of the victims have not been paid any compensation.

While this wasn't exactly a classic "old software didn't get updated, gets hacked" situation it's a lesson in the hazards of bulky, poorly-made and insufficiently-tested software - and putting faith in its infallibility.

So what's the moral of this story?

I left this section blank for three days while I considered what the actual editorial part of this editorial was to be. The Post Office's folly is comically obvious in hindsight, but what are we supposed to do with it?

I think the moral here is to remember that behind every bloated, un-upgradeable, over-priced, fully-integrated-but-barely-functioning behemoth of a software is a bunch of people who knew it was a bad idea at the time and didn't say anything.

With stories like Horizon you can imagine how it played out. An executive got sold something shiny, convinced or bullied everyone to go along with it, and left the company before it could be implemented. Nobody objected too loudly because it wasn't their circus, nor their monkeys, and they barely had control of their own monkey circuses.

Then, a cascade of failures of diligence and professional ethics compounded into a tragedy like Shakespeare guest-wrote a season of The Office.

I'm known for invoking Hanlon's Razor: the rule of thumb that you should attribute apparent negligent failures like this to incompetence, before suspecting malice. People are more likely to screw you over through stupidity than because they actually want to cause harm.

In this case I'm confident it's a rich mix of the two.

‍