Thousands of known errors on controversial Post Office computer system to be revealed

Post Office denied allegations

The Post Office has always denied the allegations about Horizon, and said there were no problems with the system that could have caused unexplained losses for subpostmasters. Leading up to the current trial, the Post Office reaffirmed its confidence in the Horizon system in a statement to Computer Weekly that said: “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.”

When subpostmasters sign a contract with the Post Office, they take on responsibility for all unexplained losses.

During cross-examination in the first trial in November, Post Office director Angela van den Bogerd admitted that the Horizon IT system had made mistakes which the Post Office was responsible for correcting, but said the Post Office did not necessarily have to tell its subpostmaster network about the errors. Van den Bogerd said the Post Office could have told subposmasters about the errors, but did not.

The known error log disclosure is part of March’s trial, the second of four currently planned, which will focus on the computer system and supporting processes at the centre of the case. The first trial, which took place in November last year, looked at the contractual relationship between subpostmasters and the Post Office. The judgment on that is expected later this month.

A third trial, scheduled for October 2019, will focus on individual subpostmasters’ claims and a fourth trial will probably be held in early 2020.

The revelation that the Horizon system has thousands of errors is no surprise to the IT community. Computer Weekly has written about the system’s problems in the past.

In November 2015, the Communication Workers Union (CWU) wrote to subpostmasters warning them of a problem with the system following an incident in which thousands of pounds’ worth of payments were duplicated for one subpostmaster.

If undetected, this would have appeared as losses when the accounts were completed, which would be the responsibility of the subpostmaster. In relation to this, Post Office IT support sent an email to a member of the postmasters’ branch of the CWU revealing the flaw.

In an email at the time, an Atos representative said this was not an isolated incident, noting: “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].”

Evidence of errors

In the first trial, the court heard evidence of errors caused by Horizon that had led to inaccurate accounts at some branches. The error was revealed in a Post Office internal memo from August 2010, which was revealed in court.

The memo said discrepancies showing at the Horizon counter disappeared when the branch followed certain process steps, but would still show in the back-end branch account. “This is currently impacting circa 40 branches since migration onto Horizon Online, with an overall cash value of circa £20k loss,” the memo said.

But the Post Office did not reveal the error to the subpostmaster network. “If widely known, it could cause a loss of confidence in the Horizon system by branches,” the internal memo said.

In a statement with regard to the trial, the Post Office said: “The Post Office is robustly defending its position in the court and welcomes the opportunity to do so. We take these cases extremely seriously and we have worked hard over a number of years to address the issues raised.

“We have conducted thorough investigations and sought to resolve some of the claims through mediation. Our employees and postmasters are important to us and we take our relationships with them very seriously.

“We have confidence in our network of 11,500 Post Office branches and the systems underpinning it. The Horizon computer system is operated successfully by thousands of employees, postmasters and their staff to process 47 million transactions every week.”

Glitches no surprise

One IT professional in the UK banking sector, who has worked on many complex computer systems, said it did not surprise him that there were thousands of glitches in a very large IT system such as Horizon.

“But I would be shocked if critical known bugs had not been addressed as soon as they were identified,” he said. “It is inevitable that some bugs and issues will get past design and testing, so the trick is to ensure the system is monitored closely in operation so that any problems can be identified and handled appropriately.”

The IT professional said users must be able to escalate any bugs they believe they have found and the system operator must manage these responsibly. “If users are not made aware of scenarios that can cause system glitches and the operator does not fix them, this is a recipe for disaster,” he added.

“Covering up a long list of known and unresolved bugs in a major system is unlikely to be forgiven by anyone if they materially affect critical functions, such as financial control and accounting.”

The subpostmasters’ case against the Post Office continues.

Separately, the Criminal Courts Review Commission (CCRC) is reviewing about 30 claims from subpostmasters that they were wrongfully prosecuted as a result of problems with the Post Office’s Horizon IT system, through which they file accounts.

The CCRC was due to announce its decisions on the cases under review, but will now wait until after the High Court judge’s ruling on the first trial in the GLO. It might then decide to wait until after the March trial.