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Clear out junk files and repair common Windows errorsFree Scan →Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →Repair Windows errors before they cause bigger problemsFix Now →Gareth Jenkins was not called as a witness in the Post Office’s 2018–19 High Court battle with 555 former subpostmasters. But according to evidence given to the Post Office Horizon IT Inquiry, lawyers still used the former Fujitsu chief architect’s technical knowledge to support other witnesses.
That apparent contradiction is why the episode has raised questions about whether Jenkins was merely kept out of a damaging cross-examination—or whether relevant evidence was effectively suppressed. The available evidence establishes the former, while the latter remains a disputed interpretation rather than a concluded legal finding.
Who was Gareth Jenkins?
Jenkins was a senior Fujitsu technical figure, described in inquiry records as a former distinguished engineer and elsewhere as a chief architect connected with the Horizon system used in Post Office branches.
He mattered because he had detailed knowledge of how Horizon operated and had previously provided evidence in criminal prosecutions of subpostmasters. That made him potentially valuable to the Post Office in litigation about whether unexplained accounting shortfalls were caused by subpostmasters or by faults in Horizon.
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It also made his credibility especially important. If an important technical witness had previously failed to disclose relevant system problems, his evidence could become a liability under cross-examination.
The inquiry has published Jenkins’s witness statements and transcripts of his evidence, including his four-day appearance from 25 June 2024 through 28 June 2024.
The 2018–19 High Court case
The Group Litigation Order was brought by 555 former subpostmasters against the Post Office. Their case challenged the assumption that accounting shortfalls necessarily resulted from theft, dishonesty or mistakes by individual branch operators. They argued that Horizon errors could produce—or contribute to—the discrepancies.
The case was a civil proceeding and was separate from the earlier criminal prosecutions in which Jenkins had given evidence. Because the reliability of Horizon was central to the dispute, a technically knowledgeable Fujitsu witness might ordinarily have been expected to play a prominent role.
Instead, Jenkins was not called.
Why did the Post Office not call him?
Anthony de Garr Robinson KC, who represented the Post Office in the group litigation, told the inquiry that the legal team considered Jenkins an unreliable witness. He said lawyers had been warned that Jenkins had previously given misleading evidence and that calling him would expose the Post Office to damaging cross-examination.
The chronology is significant:
- 2012: Jenkins gave evidence in the prosecution of Seema Misra, who was convicted and imprisoned. Her conviction was overturned in 2021.
- 2013: Barrister Simon Clarke reportedly advised the Post Office that Jenkins had failed to disclose relevant information about software errors and should not be used as an expert witness again.
- September 2018: Post Office lawyers discussed Jenkins’s reliability with de Garr Robinson before the group litigation.
- 2018–19: Jenkins was not called as a witness in the High Court case.
- 25–28 June 2024: Jenkins gave evidence to the statutory Horizon Inquiry.
The so-called Clarke Advice was a barrister’s legal advice, not itself a judicial finding that Jenkins had lied or committed an offence. But it was strategically significant: it alerted the Post Office to a serious credibility and disclosure problem before the High Court litigation.
De Garr Robinson’s account was that Jenkins would have been “disastrous” for the Post Office under cross-examination. In other words, the legal team concluded that his risks outweighed his value as a live witness.
How did Jenkins still support the Post Office’s case?
Not calling Jenkins did not mean that his technical knowledge disappeared from the litigation. According to the reported inquiry evidence, Post Office lawyers continued to consult him and used information from him to support other witnesses, including the Post Office’s chosen expert witness, Dr Robert Worden.
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1Fix the driver behind crashes, sound loss and screen glitches2Repair Windows errors before they cause bigger problems3Scan for outdated or missing drivers - takes under a minuteThat is the central tension in the episode:
- Jenkins was considered too unreliable to put in the witness box.
- His technical knowledge was nevertheless considered useful in preparing or supporting evidence from people who were called.
The phrase “supported it from the shadows” is vivid, but it should not be read as proof that Jenkins secretly controlled the Post Office’s evidence or that every part of Worden’s evidence came from him. The documented point is narrower: Jenkins was not presented as a live witness, yet remained a source of technical information for the Post Office’s legal and evidential work.
Does that amount to suppression of evidence?
Three separate propositions need to be kept apart:
- Established: Jenkins was not called as a witness in the group litigation.
- Reported from the inquiry evidence: He was still used to provide technical information to other Post Office witnesses.
- Disputed interpretation: That conduct amounted to legal suppression of evidence.
Claimants argued that failing to call Jenkins, while relying on his technical knowledge behind the scenes, could amount to suppression. De Garr Robinson rejected that characterisation. His explanation was that the Post Office made a tactical decision not to call a witness whose previous evidence could be exposed and undermined in cross-examination.
Not calling a witness is not automatically the same as unlawfully suppressing evidence. The legal questions would include what information and documents the Post Office possessed, what its disclosure duties required, whether relevant technical material was disclosed, and whether the court was given a fair opportunity to test the evidence.
The available account establishes the strategic contradiction but does not, by itself, establish a final finding that the Post Office unlawfully concealed Jenkins’s evidence. It also does not justify describing Jenkins as a proven perjurer or claiming that his evidence alone caused wrongful convictions.
Why the 2013 advice mattered
The Clarke Advice reportedly said that Jenkins had failed to give accurate or complete evidence in criminal prosecutions because he did not mention software errors of which he was aware. It reportedly recommended that he should not be used as an expert witness again.
That advice mattered for two reasons. First, it affected whether Jenkins could credibly appear as an independent technical witness. Second, it raised an obvious question about the continuing use of his knowledge after the Post Office’s lawyers had been warned about his reliability.
A person can be unsuitable as a witness while still possessing useful technical knowledge. Lawyers may consult employees or specialists to understand documents and systems without calling each person to testify. But where that person materially helps prepare another witness, the role of that person and any relevant underlying material can become important to disclosure, independence and the court’s ability to assess the evidence.
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The Seema Misra case
Jenkins gave evidence in the 2012 prosecution of Seema Misra. Her defence challenged the reliability of Horizon, including by referring to earlier reporting about system errors. Misra was convicted and imprisoned, but her conviction was eventually overturned in 2021.
Her case helps explain why Jenkins’s credibility mattered to the later High Court litigation. It does not, however, establish that Jenkins alone caused her conviction or that his evidence was the sole basis for it. The significance is that his earlier role, and what he knew about Horizon’s limitations, formed part of the credibility concerns later considered by Post Office lawyers.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What did Jenkins tell the Horizon Inquiry?
Jenkins gave evidence to the inquiry over four days beginning on 25 June 2024. The official hearing pages and witness statements cover his understanding of expert-witness duties, his involvement in criminal prosecutions, communications involving Fujitsu and the Post Office, the preparation and alteration of statements, and his knowledge of Horizon errors and system failures.
The primary records include his first, second, third and 25 June, 26 June, 27 June and 28 June 2024.
Those documents are important because they allow readers to distinguish Jenkins’s own account from the later description of him as a witness the Post Office could not safely call. They also provide the material needed to assess how he understood his responsibilities, what he knew about Horizon problems and how he interacted with other evidence.
Why the episode matters
The issue is larger than whether one witness should have entered the witness box. It concerns how technical evidence is presented when a computer system’s reliability is central to a case.
The Post Office’s position, as described by de Garr Robinson, was that calling Jenkins would have damaged its case. Yet the organisation still relied on his technical knowledge indirectly. That creates a legitimate question about whether the court and opposing parties had enough information to evaluate the origins, independence and limitations of the evidence being presented.
The episode also illustrates the difference between technical expertise and witness credibility. A person may understand a complex system exceptionally well while still being vulnerable to serious challenges about omissions, accuracy or independence. If that person helps another witness, the court may need to know enough about that assistance to assess the resulting evidence fairly.
The safest conclusion is therefore precise: Gareth Jenkins was not called in the Post Office’s High Court group litigation because its lawyers believed his credibility would collapse under cross-examination. But he was not simply removed from the case; his technical knowledge was still used to support other witnesses. Whether that crossed the line into suppression of evidence was a disputed legal question, not an established finding in the evidence identified here.
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