A senior judge has ruled glitches in the Post Office’s Horizon till system caused accounting deficits in independent stores, and that these were kept secret by the Post Office and its technology partner Fujitsu.

In Justice Fraser’s findings from the second horizon trial released this week, the judge said that not only was there a potential for bugs, errors or defects to cause discrepancies in sub postmasters’ branch accounts, but, “it actually has happened, and on numerous occasions”.

He said there were “very grave concerns” over evidence that showed that Fujitsu and the Post Office previously kept quiet about documents proving the existence of bugs to avoid it being used in “ongoing legal cases where branches are disputing the integrity of Horizon data”. It was unclear whether this related to civil cases or the more than 30 criminal cases where the Post Office was the prosecuting authority.

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Many of the retailers convicted of fraud, theft and false accounting in these criminal cases maintain that Post Office Horizon glitches were actually responsible for the crimes they were convicted of. The Criminal Cases Review Commission, which investigates potential miscarriages of justice, is expected to review whether the prosecutions brought by the Post Office against its own retailers were sound.

Justice Fraser confirmed that despite last week’s settlement of 550 sub postmasters claims against the Post Office, any retailers landed with wrongful criminal convictions maintain their rights to take the Post Office to court for malicious prosecution.

Referencing the possibility of Post Office and Fujitsu employees themselves being put before a criminal court for the evidence they had previously provided, Justice Fraser said: “I have decided to write to the director of public prosecutions, Max Hill, to see if any of these should be a matter of public prosecution.”

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Broadcast journalist Nick Wallis reported that former MP and member of the Post Office All Party Parliamentary Group Lord Arbuthnot has also called for action against the Post Office. A statement by Arbuthnot reads: “Now that these battles are being won, it is time to turn our attention to how it all came about and went so far.  

We need an inquiry and, since the Post Office has repeatedly given inaccurate information including to me, it needs to be led by a judge.”

The NFSP was again criticised in the latest court ruling. Fraser previously said the trade group was not acting independently of the Post Office in the interests of subpostmasters. The judge said the Post Office had publicly claimed its Horizon system had “the full support of the NFSP”, even though the trade group had “privately expressed its concerns.”

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Despite these private views, the NFSP had repeatedly denied there were system failures with the Horizon system and instead suggested its own members may be to blame. NFSP general secretary George Thomson told MPs at a Commons Select Committee in 2015: “I do not believe the system is systemically faulty. A lot of this is down to people making errors.”

He continued: “There are one or two issues where money went missing and postmasters have felt that it had to be Horizon, while in a lot of cases it could have been errors or, in fact, members of staff misappropriating money. Over the 15 years, the Horizon system has been fantastically robust.”

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