Faulty computer software resulted in some 230 post office workers being imprisoned on false charges of theft and fraud. Thousands of others were accused of similar misdeeds.

Mr Bates vs the Post Office: The Real Story chronicled sub-postmaster Alan Bates’s legal battle against the Post Office, which had falsely accused him and some 3,500 others of defrauding the UK’s postal service.

Following the airing of the four-part mini-series, the number of signatures on a long-running petition calling for an official honour to be stripped from former Post Office chief executive Paula Vennells rocketed to more than one million.

It had the desired effect. On Tuesday, Vennells bowed to pressure and pledged to “return my CBE with immediate effect”.

British Prime Minister Rishi Sunak has also weighed in, promising that the 700-plus postal workers who were prosecuted for crimes they never committed would “get the redress that they deserve”.

What happened?

Between 1999 and 2015, 736 Post Office branch managers were prosecuted and convicted of financial misconduct based on information generated by the organisation’s computing software. Horizon, the computer software which is still used by the Post Office today, wrongly indicated that sub-postmasters and sub-postmistresses (the official titles given to post office managers) had been involved in a campaign of theft and false accounting, leading many to serve jail time.

The miscarriage of justice came to light in 2019 when the High Court ruled that the Horizon software was to blame and the government ordered an inquiry into the affair in 2020. But, so far, only 93 people have had their convictions quashed after it was revealed that Horizon was riddled with faults. In 2021, the UK Court of Appeal overturned 39 of those convictions in a single ruling.

The rest of the cases are still being evaluated, but the recent TV drama has triggered calls for the process to be expedited.

What mistakes did the computer software make?

The Post Office began the British rollout of Horizon computing software – manufactured by the Japanese company Fujitsu – in 1999. It was introduced to manage financial transactions in the UK’s Post Office branches.

But staff soon began to report that Horizon was falsely indicating cash shortfalls and complained that the system was not fit for purpose. Their complaints to Post Office management that there were errors in the system went unheeded, and these financial irregularities continued to appear on branch accounts countrywide.

Faced with these discrepancies and lacking support from management, some sub-postmasters and sub-postmistresses attempted to plug the “financial holes” with their own money.

But Post Office chiefs, convinced that they were being defrauded and refusing to admit to Horizon’s shortcomings, began to launch private prosecutions against employees in 2000.

Some workers served prison sentences after being found guilty of theft. Many faced financial ruin after they were instructed to refund the money they were accused of stealing, and the breakdown of relationships, and several deaths by suicide have been linked to what was described by British barrister Jason Beer as “the worst miscarriage of justice in recent British legal history”.

What impact has this had on the accused postal workers?

Beer, who is counsel to the continuing public inquiry into the scandal, hearings for which officially began in February 2022, said that “reputations were destroyed, not least because the crimes of which the men and women were convicted all involved acting dishonestly.”

He added, “People who were important, respected and integral parts of the local communities that they served were in some cases shunned. A number of men and women sadly died before the state publicly recognised that they were wrongly convicted.”

Parmod Kalia was one of those wrongly imprisoned. Falsely accused of pocketing more than 20,000 pounds ($25,500 at the current rate), Kalia was given a six-month jail sentence in 2001. The southeast London postmaster had even been driven to borrow money from his mother to fill the supposed cash shortfall. But, convinced by the Horizon data, the Post Office pursued its prosecution against him. It wasn’t until 2021 that his conviction was overturned.

Seema Misra was another. The English postal worker was eight weeks pregnant when she was given a 15-month prison sentence for fraud in 2010 after she was blamed for a cash discrepancy of 74,000 pounds ($94,000 at current rate).

“I’d been warned there was a chance I could be jailed,” she recounted of her ordeal to a UK newspaper. “But I honestly just couldn’t see for a second how I could be punished like that for something I hadn’t done. I had faith in the justice system, at that point. When the judge said I’d been sentenced to 15 months’ imprisonment, I passed out. If I hadn’t been pregnant, I would have taken my own life. I was at rock bottom.”

Like Kalia, her conviction wasn’t quashed until 2021.

What will happen next?

Amid continuing political accusations that Post Office compensation payments to affected workers have been slow in coming, the TV dramatisation of the scandal has sparked new public outrage over the fact that most of those falsely accused have yet to receive justice.

The UK government is now under huge public pressure to speed up the ongoing legal process of reviewing the convictions.

The government is considering a number of options, including introducing legislation to quash all convictions of postal workers caught up in the scandal.

The next stage of the public inquiry will be a disclosure hearing in London next week, with the full timeline for the inquiry expected to stretch into the middle of this year.

Prime Minister Rishi Sunak, who was interviewed on Sunday about the affair, called the convictions an “appalling miscarriage of justice”.

Asked by the BBC’s Laura Kuenssberg whether the Post Office, which is owned by the British government, should be relieved of its role in the appeals process, he added, “Obviously, there’s legal complexity in all of those things but [we are] looking at exactly those areas that you’ve described. It is right that we find every which way we can do to try to make this right for the people who were so wrongfully treated at the time.”