Post Office’s most senior executives hushed up Horizon errors, public inquiry told

Senior Post Office executives told staff as part of its internal messaging not to reveal problems caused by its Horizon IT system, due to concerns the organisation would face serious business and legal difficulties.

During the latest public inquiry hearing into the Post Office Horizon scandal, Shaun Turner, a former executive working in the Post Office National Business Support Centre (NBSC), which supported subpostmasters using the controversial accounting system, said he was aware “as a general theme” of concerns in the organisation that if the problems were known it would cause a lack of confidence in Horizon.

Turner said he formed this opinion “largely from the messaging that was coming out of the business, particularly in the post-2009 period, around the robust nature of the Horizon system, which led to particular sensitivities around any perceived issues with the system.” In 2009, Computer Weekly published its investigation into the problems experienced by seven subpostmasters that were using Horizon.

“From my recollection the Computer Weekly article and the early days of the [campaign group] Justice for Subpostmasters Alliance were certainly things that were mentioned in the business and where messaging was coming out to internal staff, like myself, around the robust nature of Horizon.”

He said he does not remember specifically where the messages were coming from, but that they were from the top of the organisation: “My impression was that messaging was coming from senior leadership. I imagine that messaging was coming from board level down.”

Asked whether this came from as high as CEO, he said it was his impression that it did, because it was a serious concern within the business.

Turner told the inquiry that he was “certainly” told there were concerns that details of bugs could impact ongoing legal cases.

Also facing questions in the public inquiry was Gary Blackburn, former team lead at the Post Office NBSC. He said that all members of the NBSC were informed about Computer Weekly’s 2009 article concerning Horizon problems: “I think it was brought to our attention as staff members.”

“I believe that we were [then] reassured that Horizon was fit for purpose,” he said.

Blackburn agreed with Turner that the supportive messages were coming from board level. During the hearing, Blackburn was asked how he thought his seniors would have reacted if he had challenged the Post Office when it blamed subpostmasters for unexplained accounting shortfalls.

“I think the fact that I didn’t probably gives you your answer,” he said. “[The Post Office is] a highly politicised organisation, very hierarchical. I would have been seen as stepping out of line with the message and I can’t imagine that would have been good for my career. So I am sure at that point in time, which is obviously a hindsight reflection, I obviously on occasions chose to unconsciously protect myself.”

The statutory inquiry is seeking to establish what caused a scandal often referred to as the widest miscarriage of justice in UK history, which saw lives ruined as subpostmasters were blamed and punished for unexplained accounting shortfalls caused by errors in the Post Office’s Horizon computer system. The Post Office denied there were any problems with the Horizon system, whenever challenged, until a High Court judgement in 2019 proved there were errors that could cause unexplained losses.

Over 80 wrongfully prosecuted former subpostmasters have so far had convictions overturned.

An example of the messaging to staff, coming from the top of the Post Office, was revealed to the inquiry.

After the introduction of a new version, known as Horizon Online - which replaced the legacy Horizon in 2010 - a technical problem described by Post Office as the “receipts and payments mismatch issue,” was being experienced in about 40 branches. A Post Office memo to staff involved with Horizon said that affected branches appeared to have balanced their accounts, but in fact they could have a loss or gain. It also said its own accounting system will be out of sync with what was recorded at the branch.

“If widely known [the problems] could cause a loss in confidence in the Horizon system by branches,” the Post Office said in the internal memo.

The memo also said there could be a “potential impact upon ongoing legal cases where branches are disputing the integrity of Horizon data” and that “it could provide branches with ammunition to blame Horizon for future discrepancies”.  At the time, the Post Office told subpostmasters who had unexplained losses that they could not be caused by errors in the Horizon system.

The memo, from 2010, said: “Discrepancies showing at the Horizon counter disappear when the branch follows certain process steps but will still show within the back-end branch account. This is currently impacting circa 40 branches, since migration onto Horizon Online with an overall cash value of circa £20,000 loss. This issue will only occur if a branch cancels the completion of the trading period, but within the same session continues to roll into a new balance period... At this time, we have not communicated with branches affected and we do not believe they are exploiting this bug intentionally.”

The inquiry also heard about Post Office efforts to keep details of a known Horizon error, referred to as the Calendar Square bug, out of the hands of the legal representatives of subpostmaster Lee Castleton, who was in a court battle over unexplained losses

An email in December 2006, sent from a Post Office executive involved in dispute resolution to an executive from Horizon supplier Fujitsu, was marked “Calendar Square: URGENT.”

The email read: "Our legal team at the court will be doing their best to persuade the court not to allow [Lee] Castleton to call this evidence because it is filed late and does not relate to the problems at his branch. If they are successful there will be no need to progress further with these investigations, but as Castleton is a litigant in person it is common for judges to be sympathetic and may allow him to rely on this evidence. If so you will have to pull out all the stops to investigate what, if anything, went wrong at these branches and why we can distinguish them from Mr Castleton at [his branch]."

Castleton always said the losses in his accounts were caused by computer errors, but at the time he had no way of proving this. Post Office witnesses in his court case said there was no evidence of any problem with the system and that they were unable to identify any basis upon which the Horizon system could have caused Castleton's losses. The Post Office spent about £300,000 on legal costs to defeat Castleton in court to recover the shortfall. He was subsequently made bankrupt.