Sub-postmasters and sub-postmistresses were essentially used as “guinea pigs” to grind out issues within the Horizon system, an expert who first warned about the problem in 2003 has told Sky News.

IT expert Jason Coyne was instructed to examine the Horizon system in 2003 as a neutral expert witness in the Post Office’s civil case involving the Cleveleys Post Office branch in Lancashire.

He concluded in his findings that there were fundamental problems within the accounting system, developed by the Japanese multinational firm Fujitsu.

Mr Coyne said the Post Office lawyers were “disappointed” by his report and asked if they could offer new information which could change his findings.

They later opted to settle the case out of court with the branch’s sub-postmistress, Julie Wolstenholme, who had counter-claimed for unfair dismissal, meaning Mr Coyne’s report never came to light.

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The official inquiry into the Horizon scandal last year heard how a senior in-house lawyer with the Post Office had advised the company to “throw money” at keeping problems with the IT system out of the public domain.

The system – which made it appear as if money was missing from branches – was later found to be faulty, but only after more than 700 sub-postmasters and sub-postmistresses (SPMs) had been prosecuted by the Post Office based on information from the accounting system.

Mr Coyne told Sky News: “I thought it was quite clear [when making my report] that the software had some fundamental problems.

“And then when I was able to establish that the software had only been rolled out just prior to the year 2000, it was relatively clear that the software had probably rolled out too soon.

“The levels of testing or user acceptance had not been conducted properly, but instead what happened was the software was put live.

“Then the users – the sub-postmasters – were being used largely as the guinea pigs to use the system and effectively grind out problems, report them to the help desk and the problems could then be fixed in the background.”

Mr Coyne said he reached his conclusion in the report after looking through call logs between Cleveleys Post Office branch and the Horizon error logging system.

He found there had been 90 calls logged from the branch to the error logging system, 61 of which he said “clearly showed there was either a bug, error, or defect”.

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Mr Coyne said the response was often to restart the machine or that it would be replaced or updated, but that the call logs showed a number of calls reporting faults were made following those software updates.

At the inquiry last year, it was heard how Post Office managers dismissed Mr Coyne’s report as a “very one-sided view” full of general assumptions, while one lawyer described it in an internal email as “very unhelpful”.

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However, Mr Coyne said that, had his report been accepted by the Post Office, and followed up with changes, “15 to 20 years of heartache that has been laboured on the sub-postmasters might not have happened in the same way”.

“My experience was the Post Office were incredibly difficult to extract information.

“They would initially resist and say documents weren’t available, which is in stark contrast to the vast majority of other litigations that I’ve been involved in.

“Ultimately, we did get enough documents to be able to report the state of the Horizon system, but it was incredibly difficult.”

A Post Office spokesperson said: “We share fully the aims of the Public Inquiry to get to the truth of what went wrong in the past and establish accountability.

“It’s for the Inquiry to reach its own independent conclusions after consideration of all the evidence on the issues that it is examining.”

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