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Post Office misjudged campaigner it labelled a ‘bluffer’

Social media, a trade union and tech expertise helped former subpostmasters expose Post Office bug myth

Labelled a “bluffer” and an agitator, a former subpostmaster was proved right when he alerted Post Office boss Paula Vennells to a major software bug and warned that inaction would eventually see her face a judicial review.

The Post Office underestimated an ultimatum sent by Tim McCormack, who was described as a “bluffer” by a senior Post Office executive.

But if ex-CEO Vennells had listened and acted on McCormack’s warnings in 2015, she might have been spared her shameful appearance at the Post Office Horizon scandal statutory inquiry next month (May 2024).

In October 2015, McCormack wrote directly to Vennells with an ultimatum, which is now public knowledge after its appearance at the Post Office Horizon scandal inquiry. But what is less known about is the subject of the email and how he and a team of subpostmasters found proof that a software bug in Horizon was causing unexplained shortfalls in branch accounts.

Dalmellington bug

The subject of the email – the discovery of a bug at a Post Office branch in Dalmellington, Scotland – gave McCormack the ammunition to issue his ultimatum to Vennells.

At the time, the Post Office was still using the myth that Horizon was bug-free in answer to questions from subpostmasters, MPs, journalists and other campaigners. Although Computer Weekly and any IT professional knew this claim could not be true, finding evidence of errors was difficult.

In his email to Vennells, who, like the rest of the Post Office, was in denial over Horizon errors, McCormack offered to demonstrate the Dalmellington error to her. He told her of his plans to take the story to the press.

“It is a last chance for you to accept what I have been telling you these last few years is true,” he wrote. “I now have clear and unquestionable evidence of an intermittent bug in Horizon that can and does cause thousands of pounds of losses to subpostmasters.”

“Tonight, there is a branch in your network sitting on a loss of five figures,” he told Vennells. “The money does not exist. It is a result of several one-sided transactions being entered erroneously by the system, not the operator.”

He explained it was an error that would not be noticed by many subpostmasters and could well be the reason for many of the cases being highlighted by subpostmasters in the Justice for Subpostmasters Alliance (JFSA).

He gave Vennells three options: “Accept that many of the claimants in the JFSA are honest and decent citizens whose lives were destroyed by your organisation, go to the press and see what happens, or await the inevitable judicial review where you will personally be exposed and perhaps leave yourself open to criminal charges.”

Vennells will appear at the Post Office Horizon IT Inquiry for three days from 22 May.

McCormack wrote: “We can stop this farce now. You can wake up and realise that the people you rely on to tell you the truth about what is happening don’t have the ability to do so.”

This was not his first email communication with Vennells. He had previously written to her tens of times on a variety of subjects impacting subpostmasters.

He warned her that he would go to the press quickly. He told Computer Weekly he was “labelled as an agitator”.

Called a ‘bluffer’

Post Office senior lawyer Rodric Williams, who recently appeared in an inquiry hearing, replied to McCormack informing him that he had not provided enough information about the bug for the Post Office to investigate.

Williams had already told Post Office executives that he thought McCormack was a “bluffer”.

In an internal email to fellow Post Office executives, Williams said the Post Office should write to McCormack “in the same terms that we have every other person who has said they have evidence of flaws”, adding: “Generally, my view is that this guy is a buffer, who keeps expecting us to march to his tune. I don’t think we should do so, but instead respond with a straight bat.”

But McCormack wasn’t bluffing. Soon after, working with former subpostmaster and Communication Workers Union (CWU) postmaster branch chair Helen Baker, a current subpostmaster who wished to remain anonymous, and subpostmaster Mark Baker, also a CWU rep and at the time running a branch in Somerset (no relation to Helen Baker), McCormack alerted Computer Weekly to the bug. 

Computer Weekly revealed the bug in November 2015 following a rapid investigation that revealed the problem as it was happening.

The team of campaigners managed to use what they learned from a conversation on social media between two subpostmasters about problems they were having to uncover and make public the major bug. The Post Office had kept quiet about the bug and this was at a time when the JFSA was building a case against the Post Office and the latter was dismissing claims that Horizon was flawed.

The Dalmellington bug went on to be used as evidence in the 2018/19 High Court case, where Alan Bates and more than 500 other subpostmasters proved Horizon errors were to blame for accounting shortfalls.

The poor treatment of subpostmasters by the Post Office was bound to motivate campaigners, particularly those directly affected.

McCormack first got involved with campaigning during the Post Office’s network transformation in 2010, which he considered bad for his business after he and his wife had sold their small branch in the Scottish Highlands to buy a bigger branch in the Scottish borders.

The year 2010 also saw the introduction of Horizon online. McCormack told Computer Weekly his interest in Horizon errors started when he began using social media in his campaign against the network transformation.

“I got involved in using social media when campaigning, such as Yahoo! groups. I was looking at social media and was active in the National Federation of Subpostmasters (NFSP) forum,” McCormack told Computer Weekly.

“I am an inquisitive guy and I have an IT background. I just started writing to Post Office people, pointing out problems with the system; not just computer problems, but processes as well,” he added.

McCormack made suggestions to the Post Office about possible improvements and this led to him being taken relatively seriously, he told Computer Weekly. “I ended up exchanging communications with senior people at the Post Office, discussing various tech problems.

“I had seen Horizon errors reported on social media, and even ended up working with Fujitsu on one particular problem,” he added.

He had also seen Alan Bates’ campaigning website and first emailed the JFSA founder in 2013 about an error he had found.

McCormack’s work evolved. “By that time, Mark Baker, from the CWU, was a good friend and we had been campaigning against network transformation. This evolved into keeping our eyes open for Horizon errors and exchanging emails with people involved in the campaign for justice and Horizon investigations.

McCormack said he was always on the outside and was never treated seriously.

Social media sparked investigation

The investigation into what is known as the Dalmellington bug began with a social media exchange between rural subpostmasters having problems when running outreach branches, where equipment is taken to small villages to provide services.

McCormack said: “It was a Facebook post by the subpostmistress at Dalmellington on a CWU discussion. She was asking for assistance because the Post Office had not been able to help.

“There were four of us and we pounced on it,” he said.

The group found evidence that Horizon duplicated the acceptance of a remittance on at least three occasions. This was despite the payment’s barcode having only been scanned in once. This would lead Horizon to be short because the subpostmaster had repeatedly attempted to send the transfer, believing it to have failed when screen freezes forced them to log off.

“We could see it was a clear error. Helen Baker was at the time an executive officer at the NFSP and chairman of the CWU postmasters branch, so she put a certain hat on and wrote to an IT support manager. After the reply, which confirmed the problem, we sat down and came up with a plan.”

The email from an IT support worker at Post Office supplier Atos, as revealed by Computer Weekly, stated: “This issue is caused by the user forcing log-off when the post-login checks have not fully completed. We have experienced previous instances of this issue in other branches [that] have been caused in the same way (forced log-off).”

The Atos employee said the problem was a process issue that would require a code change from Fujitsu. The email said subpostmasters had not been warned about the bug.

The error was an important find, as was the confirmation that a bug could cause thousands of pounds worth of shortfalls in a branch’s accounts, which the subpostmaster would not necessarily notice until they did their accounts. The Post Office held subpostmasters responsible for any shortfalls that couldn’t be explained.

At the time, the Post Office was still denying there were bugs that could cause unexplained shortages, but Dalmellington was proof a bug did exist.

The Post Office scandal was first exposed by Computer Weekly in 2009, revealing the stories of seven subpostmasters and the problems they suffered due to accounting software (see timeline of Computer Weekly articles about the scandal below).

• Also read: What you need to know about the Horizon scandal

• Also watch: ITV’s documentary – Mr Bates vs The Post Office: The real story

Read all Computer Weekly articles about the scandal since 2009 since 2009

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