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https://www.theguardian.com/uk-news/2024/jan/09/how-the-post-offices-horizon-system-failed-a-technical-breakdown https://www.theguardian.com/uk-news/2024/jan/09

https://www.theguardian.com/uk-news/2024/jan/09/how-the-post-offices-horizon-system-failed-a-technical-breakdown https://www.theguardian.com/uk-news/2024/jan/09/how-the-post... > One, named the “Dalmellington Bug”, after the village in Scotland where a post office operator first fell prey to it, would see the screen freeze as the user was attempting to confirm receipt of cash. Each time the user pressed “enter” on the frozen screen, it would silently update the record. In Dalmellington, that bug created a £24,000 discrepancy, which the Post Office tried to hold the post office operator responsible for. > Another bug, called the Callendar Square bug – again named after the first branch found to have been affected by it – created duplicate transactions due to an error in the database underpinning the system: despite being clear duplicates, the post office operator was again held responsible for the errors. There isn't a full list of the bugs produced, but it does look like a lot of bugs directly involved incorrect accounting to be recorded.

cge 3y ago
I had assumed that bugs allowing such miscarriages of justice would require a completely unsound accounting method in the software. Unless, eg, the accounting simply didn't store a transaction ledger and software didn't store logs, and instead mostly just updated balances with no history, it was unclear to me how software bugs in an otherwise reasonably sound accounting method could result in accounting so wrong that it couldn't seen to be incorrect when investigated at the level of thoroughness one might expect for court proceedings. But these bugs suggest that at least some of the errors would likely have been obvious in a ledger, and the Post Office simply didn't care. That rather makes Fujitsu look not quite as bad here, and the Post Office look worse.

cge 3y ago

I had assumed that bugs allowing such miscarriages of justice would require a completely unsound accounting method in the software. Unless, eg, the accounting simply didn't store a transaction ledger and software didn't store logs, and instead mostly just updated balances with no history, it was unclear to me how software bugs in an otherwise reasonably sound accounting method could result in accounting so wrong that it couldn't seen to be incorrect when investigated at the level of thoroughness one might expect for court proceedings. But these bugs suggest that at least some of the errors would likely have been obvious in a ledger, and the Post Office simply didn't care. That rather makes Fujitsu look not quite as bad here, and the Post Office look worse.