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Post Office trial throws up known problem with Horizon system

High Court case in which subpostmasters are suing the Post Office has revealed a known problem with the computer system at the core of the dispute

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

May 2009: Bankruptcy, prosecution and disrupted livelihoods – postmasters tell their story

September 2009: Postmasters form action group after accounts shortfall

November 2009: Post Office theft case deferred over IT questions

February 2011: Post Office faces legal action over alleged accounting system failures

October 2011: 85 subpostmasters seek legal support in claims against Post Office computer system

June 2012: Post Office launches external review of system at centre of legal disputes

January 2013: Post Office admits Horizon system needs more investigation

January 2013: Post Office announces amnesty for Horizon evidence

January 2013: Post Office wants to get to bottom of IT system allegations

June 2013: Investigation into Post Office accounting system to drill down on strongest cases

July 2013: Post Office Horizon system investigation reveals concerns

October 2013: End in sight for subpostmaster claims against Post Office’s Horizon accounting system

October 2013: Former Lord Justice of Appeal Hooper joins Post Office Horizon investigation

November 2013: 150 subpostmasters file claims over “faulty” Horizon accounting system

September 2014: Fresh questions raised over Post Office IT system’s role in fraud cases

December 2014: MPs blast Post Office over IT system investigation and remove backing

December 2014: Why MPs lost faith in the Post Office’s IT investigation, but vowed to fight on

December 2014: MPs to debate subpostmaster IT injustice claims

December 2014: MP accuses Post Office of acting “duplicitously” in IT investigation

January 2015: MPs force inquiry into Post Office subpostmaster mediation scheme

January 2015: Post Office faces grilling by MPs over Horizon accounting system

February 2015: Post Office CIO would talk to any subpostmaster about IT problems, promises CEO

March 2015: Post Office ends working group for IT system investigation day before potentially damaging report

March 2015: MPs seek reassurance over Post Office mediation scheme

March 2015: Retiring MP aims to uncover truth of alleged Post Office computer system problems

April 2015: Post Office failed to investigate account shortfalls before legal action, report claims

April 2015: Criminal Courts Review Commission set to review subpostmasters’ claims of wrongful prosecution

May 2015: IT system related to subpostmaster prosecutions under review by CCRC

June 2015: Post Office looking to replace controversial Horizon system with IBM, says MP

July 2015: Campaigners call for independent inquiry into Post Office Horizon IT system dispute

October 2015: James Arbuthnot takes Post Office IT fight to House of Lords

November 2015: The union that represents Post Office subpostmasters has warned of a problem with the Horizon accounting system

November 2015: An email from Post Office IT support reveals a problem with the Horizon system and supporting processes that could lead to accounting errors

November 2015: Group litigation against Post Office being prepared in Horizon dispute

February 2016: Post Office faces group litigation over Horizon IT as subpostmasters fund class action

June 2016: Post Office chairman Tim Parker says there would be “considerable risk” associated with changing its Horizon computer system

November 2016: The legal team hired by a group of subpostmasters will take their case to the next stage

January 2017: The group action against the Post Office that alleges subpostmasters have been wrongly punished for accounting errors gets a green light from the High Court of Justice

March 2017: 1,000 subpostmasters apply to join IT-related group litigation against Post Office

April 2017: Investigation into claims of miscarriages of justice in relation to a Post Office accounting system has appointed a forensic accountant firm

May 2017: Hundreds of subpostmasters have applied to join IT-related legal action since March

July 2017: Post Office defence in computer system legal case due this week

August 2017: Campaigners submit initial evidence in group litigation against Post Office over controversial Horizon IT system

October 2017: Subpostmasters’ group action against the Post Office reaches an important milestone

November 2017: An end is in sight for subpostmasters’ campaign against alleged wrongful prosecution, which they blame on a faulty computer system

November 2017: The high court judge managing the subpostmasters versus Post Office legal case over an allegedly faulty computer system tells legal teams to cooperate

January 2018: Forensic investigation into Post Office IT system at centre of legal case nears completion

April 2018: Criminal Cases Review Commission forensic examination of the IT system at the centre of a legal case against the Post Office has raised further questions

May 2018: Post Office branches unable to connect to Horizon computer system for several hours after morning opening time

Oct 2018: After over a decade of controversy, next week marks the beginning of a court battle between subpostmasters and the Post Office

November 2018: Case against Post Office in relation to allegedly faulty computer system begins in High Court

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