AS a retired accountant who spent much of much of his career in systems development and implementation, I read Andrew Tickell’s article in last weekend’s Sunday National (Testimonies of ripped-off Post Office staff highlight reckless greed, May 15) with interest and mounting rage. Not, I hasten to add, at his excellent reporting, but at the egregious criminal behaviour of the Post Office and the developer of its now notorious software, Horizon.

Mr Tickell didn’t identify the supplier of the software, but it’s widely in the public domain: Fujitsu.

At its core, Horizon is a bog-standard point-of-sale double-entry bookkeeping system, so every debit booked must have an equal and opposite credit entry. It is therefore self-balancing. The faults therefore must have arisen in the system reports produced by Horizon from the core ledger data.

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That the faults were not discovered before implementation tells me that neither Fujitsu nor the Post Office tested the application adequately. This is a primary one level failure of project management by both parties with horrendous consequences for postmasters and their staff and – given that lives were lost, people were bankrupted and imprisoned – criminal prosecutions should follow.

Routine rigorous testing by both Fujitsu and the Post Office would have identified the presence of bugs in the system, but the facts are that the system went live without their identification and eradication.

This leads to the conclusion that Fujitsu either released a product without fully understanding its flaws, or they did understand them but went ahead with its release anyway. Likewise, the Post Office either installed and operated the system without knowing it was flawed, or did know it had flaws but went ahead with implementation and operation despite this.

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Either way, both parties are grossly negligent. However it was the Post Office’s relentless and ruthless pursuit of postmasters and their staff that became the major scandal. Over time the system threw up more and more deficits and yet neither the Post Office nor Fujitsu ever made any serious effort to understand why. The sheer scale of the Post Office’s persecution of the victims has kept Fujitsu out of the limelight, but in normal circumstances the client would sue the pants off a software supplier which installed a defective system.

That hasn’t happened here partly because the Post Office’s behaviour has been seen as the major problem requiring immediate action, but the Met is known to be investigating Fujitsu’s role in the matter, so further criminal charges are possible.

One other thing sticks out a mile: there are hundreds of cases of the system producing deficits (false negatives), but not one about false positives. If the faults result from an intermittent bug, we should expect it to produce false positives too. Their absence leads to an even more chilling thought which got my old “auditor’s nose” twitching in alarm: was the system designed to produce deficits?

Ken Mathieson

HAMISH Morrison’s report of specialist teams given the powers of arrest over welfare fraud stinks of Thatcher snoopers and Nazi Germany (Welfare staff given new powers to arrest fraud claimants, May 20). How many Tories involved in cash for honours, PPE fraud, tax avoidance and offshore accounts have been arrested? This is dangerous stuff, with the Tories’ demolition of human rights and more to come. Or is it a case of the empire strikes back?

Glen Peters