The Case of Rev. Bayes v The Post Office

Like almost everyone that’s seen the story of Mr Bates and the Post Office, I’m horrified that so much harm has been done to so many by so few.

The ease with which powerful people believed the stories of other powerful people in the absence of evidence is awful. 

But… What systematic methods of thinking or deduction could our government have used to expose the injustice at a much earlier stage? 

With this question in mind, I turned my head away from Paula Vennells and towards another minister who, by contrast, did have remarkable skills of deductive reasoning and in fact, invented a whole new area of statistics. Reverend Bayes died over 260 years ago and the Bayes Theorem is named after him. Simply put, it means we should update our assumptions of how likely a thing is as new evidence about that thing comes to light. 

How might it apply in this case of Mr Bates and The Post Office?

Well, we can reframe Bayes to create another two lenses to view this sorry world:

  • What would it look like if Alan Bates had stolen the money?
  • What would it look like if Alan Bates had not stolen the money?

What would it look like if Alan Bates had stolen the money?

  • Well, there would be some evidence of it and as I’ve heard plenty of times in American crime fiction, we should: “Follow the money”. The only evidenced flow of money seems to have been out of the pockets and life savings of the accused and into the coffers of the Post Office and their suppliers. If you look for it and can’t find it, that is new evidence and should be taken into account when re-evaluating the likelihood that Alan Bates did steal the money. 
  • The Post Office would be trying to win in court by showing complete transparency and getting all the facts on the table for all to see
  • This one is less certain, but I suspect Mr Bates would have concealed his actions slightly more skilfully than he did. If we try to put ourselves in his shoes and assume for a moment that we are guilty… Then we might bag up the cash ready to put it under our mattresses but as we’re cashing up for the day, the system says: “the numbers don’t tally”. Unless we’re  ready to skip the country with tickets already purchased and a new life planned out in detail, the simplest thing would be to take the money out of the bag and put it back in the till! But he didn’t do that! He drew everyone’s attention to it. He doesn’t seem like a ruthless genius, taunting his pursuers. He seems like a nice guy that can’t stop doing what he has always done: take care of the details, think things through and acting with integrity.

What would it look like if Alan Bates had not stolen the money?

  • It would look like he wasn’t benefiting from the money
  • It might look like the Post Office were trying to defeat their opponents by:
    • Attrition
    • Shock and awe 
    • Misdirection
    • Technicalities 
  • If he was not easily intimidated, Mr Bates would stand his ground and refuse to say that he had done anything wrong
  • It would look like the Post Office and their suppliers were either lying, incompetent, or both
    • Saying that there are no others experiencing the same problems
    • Saying that a system is infallible
    • Openly stating that they have a responsibility to protect the brand of the Post Office 
    • Stating it’s impossible for anyone other than the operator of the Horizon system at the Sub Post Office premises to alter or create a transaction
    • Hiding, refusing to hand over or redacting key documents 

Of course this isn’t an exhaustive analysis, rather it’s just a quick skim over the top. Others (Private Eye and Computer Weekly for instance) have been all over this travesty for years. 

But sometimes, it’s really valuable to dispassionately look at the evidence we have and consider if it could support any other hypothesis but the one we’ve been clinging to. 

And then approaching it from that perspective to say: If this alternate hypothesis was true, what else should I be seeing?

Finally, if you’re worried that your business might have been barking up the wrong tree and performing mental gymnastics to make the evidence fit the pet hypothesis, please give me a call!


I’m sure you won’t be surprised that I use ChatGPT to create visuals for my blogs. I’m truly astonished how it’s able to give me unique images that reflect the points I’m trying to make. Before I settled on The Reverend Bayes doing battle with a red dragon, I was exploring the idea of a dog barking up the wrong tree. 

I liked the idea but in the end decided against it. But I still liked the image so decided to introduce an entirely unnecessary epilogue just so I had an excuse to include the image! I hope you enjoy it as much as I do!