CoRecursive: Coding Stories

Host: Adam Gordon Bell
Episode: Story: Risk Rolls Downhill – The Software Bug That Sent People to Prison
Date: October 2, 2025
Guest: Scott Darlington, former UK Post Office sub-postmaster

Episode Overview

In this gripping episode, Adam Gordon Bell delves into the human cost of software failure through the story of Scott Darlington, a UK sub-postmaster whose life was derailed by a bug-ridden accounting system called Horizon. What starts as an optimistic tale of small business ownership spirals into a cautionary account of institutional denial, software bugs, and misplaced trust in computers—culminating in financial ruin, criminal charges, and a decades-long fight for justice.

Theme:
When society places more trust in computer systems than in people, the consequences can be devastating. This episode explores the ethical and personal dimensions of software failures, focusing on responsibility, culture, and the burden of risk in large organizations.

Key Discussion Points and Insights

1. Scott’s Optimism and Decision to Run a Post Office

• Scott portrayed as an upbeat, ambitious person, hoping for stability for his family by running a rural post office.
• He invested personal savings and family money after careful research, describing the post office as "a job that he could actually look forward to and a job with a future that he could count on" ([02:54] A).

2. Introduction and Problems with Horizon Software

• Horizon was a legacy, clunky system running on outdated Windows NT infrastructure, with Microsoft maintaining it under a special contract.
  • “Nobody could understand the software too well. It was very clunky. It was Windows NT, which even in 2005 was old.” ([04:23] B)
• Despite being “void by then,” the system was still widely used due to high costs of replacement.

3. Financial Realities and Reliance on Perfection

• A typical branch handled enormous amounts of money, demanding monthly reconciliations with zero tolerance for discrepancies.
  • "In a typical week, 100 to 150,000 pounds moved across that counter." ([05:15] A)

4. The Bug Bites: Scott’s Discrepancies Begin

• Early after taking over, Scott inherited a £600 discrepancy, but larger problems soon appeared: a £1,750 shortfall in stamps the system claimed to exist but didn’t.
  • "In 2008, suddenly the system said I was 1750 pounds out." ([06:39] B)
  • “The system has to be set so it's exact, so it can cut off that period and start a new period ... but it can't do until any discrepancies are resolved.” ([07:26] B)

5. No Redress, No Recourse: The System’s Word is Law

• Scott’s pleas for support go unheeded; the policy is simply that he must pay any shortfall the computer reports, with no path for escalation or real investigation.
  • "If the system says that you owe us 1750, so we can take it out of your pay either in one payment or two." ([07:54] A)
• Small mistakes quickly snowball, as Scott is forced to falsify records to keep the business operational—eventually racking up a supposed debt of £44,000.

6. Desperation and Inevitable Collapse

• Scott faced the dilemma: report a deficit and go out of business, or falsify records and hope the system rights itself. The gap grew inexorably.
  • "So he says he has the money, he'll figure it out later, but then ... now he's out £9,000, and then the next day ... before he knows it, he's £44,000 short." ([11:00] A)

7. Audit, Prosecution, and Institutional Injustice

• An audit triggers prosecution with no genuine investigation into the systemic issues.
  • "I was pleased that the auditor was there because I thought ... errors would come to light. But they never did the slightest bit of investigation. They just immediately started prosecution proceedings." ([13:15] B)
• Scott is charged with multiple counts of false accounting and threatened with imprisonment.
  • "They just presumed you'd nicked it, presume you've stolen it. They didn't listen to any explanations." ([14:16] B)

8. The Technology Failure: Known Bugs and Organizational Secrecy

• Adam recounts known bugs (“Calendar Square”, “remming out bug”) that caused duplication or mismatch of stock and cash—documented and recognized within Fujitsu, but never disclosed to the operators.
  • “Fujitsu engineers had already had a name for a bug that seemed a lot like the one that was draining his account ... Calendar Square ... but the subpostmasters were never warned.” ([28:17] A)
• Fujitsu kept a list of known errors hidden, neither alerting postmasters nor the Post Office.

9. Systemic Organizational Failures and the Culture of Blame

• The institution’s structure channeled all risk and blame downward to those least able to resist: the subpostmasters.
  • "Risk rolls downhill. If a ledger goes wrong, the people with the least power end up holding the bag." ([41:08] A)
• Support lines merely worked through scripts, never escalating to real investigation or accountability.

10. Personal and Community Fallout

• Scott describes the immense shame, isolation, and financial destruction:
  • “I’m on the newspaper ... as this crooked postmaster. Dishonest postmaster ... Luckily, the people that knew me, they knew something wasn’t right. But the wider public ... presumed I’d been up to no good.” ([43:52] B)
  • He lost his business, nearly lost his home, suffered years of unemployment, and struggled with stigma and mental health.
    • “I couldn’t get a job ... you have to say if you’ve got any criminal convictions ... I’d gone from earning pretty good money ... to state benefits, unable to find a job for three and a half years. And I got an eight-year old daughter at this time.” ([45:25] B)

11. The Slow March to Justice

• Only many years later, through persistent journalism and a public inquiry, did the truth about Horizon’s flaws and the Post Office’s misconduct become widely known.
  • 555 subpostmasters sued the Post Office (2017–2019) and won, but many (including Scott) received no compensation due to their convictions.
  • “You plead guilty, you get nothing. But then in 2024, a TV drama scandal caught the attention of the Prime Minister and now new legislation is probably going to overturn Scott's conviction ... but it hasn't happened yet.” ([50:15] A)

12. Moral and Professional Lessons for Software Developers

• Adam reflects on how responsibility and risk are often foisted onto those least able to defend themselves, cautioning listeners to speak up if they see harm being done by the systems they build or maintain.
  • “Even in our commercial endeavors, we need to sometimes take the corporate blinders off ... If someone is going to jail because of a software bug ... that matters because these risks often roll downhill.” ([47:37] A)

Notable Quotes & Moments

• “Nobody could understand the software too well. It was very clunky. It was Windows NT, which even in 2005 was old.” – Scott Darlington, [04:23]
• “All of a sudden, he's just total stress, you know, total stress and anxiety. Because I know that I'm in trouble as well, and not just financial trouble, but I know that I'm going to be in trouble ...” – Scott Darlington, [11:56]
• “The contract said we're reliable, and that was it. They knew that they'd go to court on that, and they did go to court on that.” – Scott Darlington, [12:26]
• “They just presumed you'd nicked it, you know, presume you've stolen it. They didn't listen to any explanations ...” – Scott Darlington, [14:16]
• “Risk rolls downhill. If a ledger goes wrong, the people with the least power end up holding the bag because they can't prove who's at fault.” – Adam Gordon Bell, [41:08]
• "I had to plead guilty to false accounting, otherwise I would be going to prison because the judge would have just said, well, you did leave false accounting, you know ... I really did think that it would come to my aid in the end, but it didn't." – Scott Darlington, [42:57]
• "I don't know how they could sleep at night ... in big corporations, it appears that there's this kind of group think mindset ... people just do not. They just don't rock the boat." – Scott Darlington, [47:13]
• “They can’t load the risk of their systems onto other people, which is what they did. Every system’s got faults. … But instead there was none of that, and off to prison we went.” – Scott Darlington, [49:18]
• “Oh, yeah, I don’t go. I don’t even like the vans going past with the sign on the side ... I hate the thought of it, really.” – Scott Darlington, [51:07]

Timestamps for Key Segments

| Timestamp | Topic | |-----------|-------| | 00:00–01:36 | Introduction, theme setup | | 01:36–04:23 | Scott’s background and decision to buy the Post Office | | 04:23–06:39 | The Horizon system and its legacy flaws | | 06:39–09:51 | Early discrepancies and the beginnings of financial trouble | | 09:51–11:56 | Scott resorts to false accounting, the situation spirals | | 12:54–15:06 | Audit, prosecution, and lack of recourse | | 16:15–17:12 | Legal system’s tilt, charges, and Scott’s experience in court | | 17:12–32:00 | Technical deep dive: Horizon bugs, known error logs, remming out, double entries | | 32:00–41:08 | Organizational culture, risk allocation, and institutional blame | | 41:08–47:13 | Outcomes for Scott and others; reflection on the role of software and organizations | | 47:13–49:18 | Adam’s call for responsibility and whistleblowing in tech | | 50:15–51:07 | Latest legal updates, slow progress toward exoneration and compensation | | 51:07–51:42 | Scott’s lingering trauma and aversion to the Post Office | | 53:36–End | Scott’s music, closing notes |

Conclusion & Takeaways

This episode masterfully illustrates how software can amplify institutional flaws and harm individuals whose means to respond are constrained. It’s a call for empathy, accountability, and vigilance—for software engineers, institutions, and anyone who participates in systems affecting people’s lives.

Technical lesson: Software bugs combined with opaque support systems and institutional denial can create Kafkaesque nightmares for ordinary people.
Ethical lesson: When problems occur, risk “rolls downhill,” placing the greatest burden on those least equipped to address systemic flaws.
Professional lesson: If you see a pattern of harm from systems you build or maintain, speak up—the world needs more people willing to "rock the boat" for what’s right.

For further exploration:

• Scott's book: “Signed, Sealed, Destroyed”
• TV Drama: “Mr. Bates vs the Post Office”
• Computer Weekly’s investigative reporting on the Horizon scandal

[End of summary]