“The Great Post Office Scandal” (Nick Wallis)

I’ve been following the story of the UK Post Office and its dubious prosecutions of sub-postmasters based on “evidence” of their wrongdoings from its IT system, Horizon, for some years.

My mother worked in the Post Office all of her working life and I also used to work there part-time during school and university holidays. There were no computer terminals on the counters back then; it was all very much paper trail accounting and I remember working on the big ledger when it came to balancing the weekly account every Wednesday afternoon (a process that often continued well into the evening).

Nick Wallis’s book covers the story in incredible detail, describing how the Post Office’s Horizon system (built by Fujitsu under an outsourcing arrangement) was badly managed by both the Post Office and Fujitsu (along with poor Government oversight) and resulted in thousands of innocent people having their lives turned upside down. It is both a moving account of the personal costs shouldered by so many individuals as well as being a reference piece for all of us in IT when it comes to governance, the importance of taking bugs seriously, and having the courage to speak up even if the implications of doing so might be personally difficult.

It’s amazing to think this story might never have been told – and justice never been served – were it not for a few heroes who stepped up, made their voices heard and fought to have the truth exposed. The author’s dedication to telling this story is commendable and he’s done an incredible job of documenting the many travesties that comprise the full awfulness of this sorry tale. This case is yet another example of the truth of Margaret Read’s quote:

Never doubt that a small group of thoughtful, committed citizens can change the world; indeed, it’s the only thing that ever has.

One of the more surprising aspects of the story for me was the fact that very complex IT systems like Horizon have been considered in UK law (since 1990) to be “mechanical instruments” and they’re assumed to be working correctly unless shown otherwise. This was a key factor in the data shown by Horizon being trusted over the word of sub-postmasters (many of whom had been in the loyal service of the Post Office in small communities for decades).

Jones wanted the Law Commission’s legal presumption (that ‘in the absence of evidence to the contrary, the courts will presume that mechanical instruments were in order at the material time’ [from 1990]) modified to reflect reality. He told the minister, ‘If people found it difficult to prove a computer was operating reliably in the early 1990s, we can only imagine how difficult it might be to do that today, with the likes of machine-learning algorithms coming to conclusions for reasons even the computer programmer doesn’t understand.’

Darren Jones, chair of the BEIS Select Committee, p. 456 of “The Great Post Office Scandal”

It’s now clear that the complex systems we all build and engage with today (and even back when Horizon was first rolled out) have emergent behaviours that we can’t be predicted. The Post Office’s continued denial that there were any bugs in Horizon (and Fujitsu’s lack of co-operation in providing the evidence to the contrary) seems utterly ridiculous – and it was this denial that allowed so many miscarriages of justice in prosecuting people based on the claimed infallibility of Horizon.

Program testing can be used to show the presence of bugs, but never to show their absence!

Edsger W. Dijkstra

Reading this story really made me think about what the onus on testers is in terms of revealing important problems and advocating for them to be addressed. The tragic cases described in the book illustrate how important it is for testing to be focused on finding important problems in the software under test, not just proving that it passes some big suite of algorithmic checks. Fujitsu, under duress, eventually had to disclose sets of bug reports from the Horizon system and acknowledged that there were known bugs that could have resulted in the balance discrepancies that resulted in so many prosecutions for theft. There are of course much bigger questions to be answered as to why these bugs didn’t get fixed. As a tester raising an issue, there’s only so far you can go in advocating for that issue to be addressed and your ability to do that is highly context-dependent. In this case, even if the testers were doing a great job of finding and raising important problems and advocating for them to be fixed, the toxic swill of Fujitsu, Post Office and government in which everyone was swimming obviously made it very difficult for those problems to get the attention they deserved.

Coming back to my anchors that are the principles of context-driven testing, these seem particularly relevant:

• People, working together, are the most important part of any project’s context.
• Projects unfold over time in ways that are often not predictable.
• Only through judgment and skill, exercised cooperatively throughout the entire project, are we able to do the right things at the right times to effectively test our products.

I think part of our job as testers is not only to test the software, but also to test the project and the processes that form the context around our development of the software. Pointing out problems in the project is no easy task, especially in some contexts. But, by bearing in mind cases like the Post Office scandal, maybe we can all find more courage to speak up and share our concerns – doing so could quite literally be the difference between life and death for someone negatively impacted by the system we’re working on.

It would be remiss of me not to mention the amazing work of James Christie in discussing many aspects of the Post Office scandal, bringing his unique experience in both auditing and software testing to dig deep into the issues at hand. I strongly encourage you to read his many blog posts on this story (noting that he has also written an excellent review of the book).

“The Great Post Office Scandal” is available direct from the publisher and the author maintains the Post Office Scandal website to share all the latest news of what is, incredibly, still an ongoing story.

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