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Evidence presented in the High Court has revealed a previously undisclosed problem with the Horizon computer system at the centre of a decade long dispute between the Post Office and a group of subpostmasters.
Alleged fallibilities of the Horizon system, which has been used in thousands of post offices since its introduction in 1999/2000, are at the centre of the group litigation order being heard.
More than 500 former subpostmasters are seeking damages for the suffering they experienced after some were heavily fined, had to pay back thousands of pounds in shortfalls, and in some cases were sent to prison because of unexplained discrepancies in accounts. They blame the Horizon system for the errors (see timeline below for all Computer Weekly coverage).
In 2009, Computer Weekly revealed the stories of some subpostmasters, who had received heavy fines and even jail terms for alleged false accounting, which they blamed on Horizon.
Leading up to the current trial, the Post Office reaffirmed its confidence in the Horizon system in a statement to Computer Weekly. “We have confidence in the Horizon system, which is robust, reliable and used across 11,500 branches by postmasters, agents and their many thousands of staff to process millions of transactions successfully every day, including on behalf of the UK’s high street banks,” it said.
The trial, which began on 7 November, is focused on the contractual relationship between subpostmasters and the Post Office. Horizon will be the focus of a further trial in March next year.
But in documents referred to in court and written about by broadcast journalist Nick Wallis in his Post Office trial blog, evidence of a known problem with Horizon is described by the Post Office and its IT partner Fujitsu.
A Post Office internal memo from August 2010, referred to in court and entitled Receipts payments mismatch issue memo day 1 OP_0008387, reveals that discrepancies showing at the Horizon counter disappear when the branch follows certain process steps, but will still show within the back-end branch account.
Only a small number of branches were known to have been affected at the time, according to the memo. “This is currently impacting circa 40 branches since migration onto Horizon Online, with an overall cash value of circa £20k loss,” the memo said. “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.”
The memo revealed that the Post Office had not communicated with branches affected at the time and did not believe they were “exploiting this bug intentionally”.
“The problem occurs as part of the process when moving discrepancies on the Horizon system into local suspense,” it said. “When discrepancies are found during stock unit rollover into a new transaction period, then the user is asked if the discrepancy should be moved to local suspense.
“If the branch presses cancel at this point, the discrepancy is zeroed on the Horizon system.”
But the document said this is not fed into Post Office systems, which still show a discrepancy while the branch system does not.
Out of sync
The memo said the branch will appear to have balanced its accounts, but in fact it could have a loss or gain, and the Post Office’s accounting system will be out of sync with what is recorded at the branch.
It added that this issue could be damaging if revealed. “If widely known, it could cause a loss of confidence in the Horizon system,” the memo said. “There could be a potential impact upon ongoing legal cases where branches are disputing the integrity of Horizon data. It could provide branches with ammunition to blame Horizon for future discrepancies.”
The remedy to the problem recommended in the memo involved the Post Office “explaining the reason for a debt recovery/refund, even though there is no discrepancy at the branch”. It said the risk associated with this was that it could “potentially highlight to branches that Horizon can lose data”.
This is not the only example of known issues with Horizon. In 2015, Computer Weekly revealed the contents of an email to a postmaster from the company that provided IT support to the Post Office about a case of duplicated payments. It described the problem, and said it had happened before.
In the email, which Computer Weekly had seen, an Atos representative said: “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 Horizon supplier Fujitsu to stop it happening again across the network. The email said the code change was planned.
“The ability for this to occur can be addressed by a code change that will avoid further instances of this across the estate,” it said.
At the current trial, judge Mr Justice Fraser has so far heard opening statements from the QC for the claimants, Patrick Green, and David Cavender, QC for the defence. Lead claimant Alan Bates took the stand to be cross-examined on his 41-page witness statement.
Bates was a subpostmaster at Craig-y-don, Wales, from 1998 to 2003, and went on to create a campaign group known as the Justice for Subpostmasters Alliance, mounting a campaign that brought about this week’s trial.
Former subpostmasters Pam Stubbs and Mohammad Sabir, also lead claimants, were also questioned in court.
The case continues.
Timeline of the Post Office Horizon case since Computer Weekly published its first article in 2009
September 2009: Postmasters form action group after accounts shortfall
November 2009: Post Office theft case deferred over IT questions
January 2013: Post Office announces amnesty for Horizon evidence
December 2014: MPs to debate subpostmaster IT injustice claims