Post Office scandal explained: What the Horizon saga is all about

Senior figures from the Post Office, the technology firm Fujitsu and the government are facing questions about what has been called the biggest miscarriage of justice in UK history.

Hundreds of sub-postmasters and postmistresses were wrongly prosecuted after faulty computer software calculated that money was missing from post office branches.

The government has promised to quash their convictions and pay compensation.

More than 900 sub-postmasters and postmistresses were prosecuted for stealing money because of incorrect information provided by a computer system called Horizon.

The Post Office itself brought many of the cases to court, and between 1999 and 2015, it prosecuted 700 people - an average of one person a week.

Another 283 cases were brought by other bodies, including the Crown Prosecution Service (CPS).

Many of those convicted went to prison for false accounting and theft. Many were financially ruined.

In 2017, a group of 555 sub-postmasters took legal action against the Post Office. In 2019, it agreed to pay them £58m in compensation, but much of the money they received was swallowed up by legal fees.

Although campaigners won the right to have their cases reconsidered, as at 15 January 2024, only 95 convictions had been overturned.

The Metropolitan Police is also investigating the Post Office over potential fraud offences arising from the prosecutions.

A public inquiry began in February 2021, chaired by Sir Wyn Williams.

The Criminal Cases Review Commission (CCRC) said the scandal was "the most widespread miscarriage of justice the CCRC has ever seen, and represents the biggest single series of wrongful convictions in British legal history".

The issue was highlighted by the ITV drama Mr Bates vs the Post Office, which was broadcast in January 2024.

Horizon was developed by the Japanese company Fujitsu, for tasks such as accounting and stocktaking. It was introduced by the Post Office in 1999.

Sub-postmasters quickly complained about bugs in the system after it falsely reported shortfalls - often for many thousands of pounds.

The Horizon system is still used by the Post Office, which describes the latest version as "robust".

Many former sub-postmasters and sub-postmistresses say the scandal ruined their lives.

Some used their own money to cover non-existent shortfalls because their contracts with the Post Office stated they were responsible for any unexplained loss. Many faced bankruptcy or lost their livelihoods.

Marriages broke down, and some families believe the stress led to debilitating health conditions, addiction and even premature death.

Days after the ITV drama was broadcast, the government announced plans to "swiftly exonerate and compensate" those affected.

Victims will be able to sign a form to say they are innocent, in order to have their convictions overturned and claim compensation.

Downing Street said it would work with Scotland and Northern Ireland to ensure the people who were wrongly accused in those nations would also be cleared.

Post Office Minister Kevin Hollinrake said the government has budgeted £1bn for compensation.

More than 4,000 people have been told they are eligible, under three separate schemes:

Prof Chris Hodges, chair of the the independent Horizon Compensation Advisory Board, told the BBC that some individual compensation claims were "well over £1m".

The Post Office is owned by the government. However, the Post Office Ltd board is responsible for day-to-day operations.

Former Post Office chief executive Paula Vennell resigned in 2019 over the scandal. In January 2024, she said she would hand back her CBE after a petition calling for its removal gathered more than a million signatures.

In August 2023, current chief executive Nick Read said he would return all of the bonus money he had received for his work on the Horizon inquiry. He apologised for "the procedural and governance mistakes made".

Fujitsu Europe director Paul Patterson told the Post Office inquiry that his firm had "clearly let society down". He previously told MPs that Fujitsu had a "moral obligation" to help fund compensation payments.

Lib Dem leader Sir Ed Davey has been criticised for refusing to meet Alan Bates, the sub-postmaster who led the campaign to expose the scandal, when he was postal affairs minister in May 2010. He says he was "deeply misled by Post Office executives".

The BBC has discovered that former Prime Minister David Cameron's government knew the Post Office had dropped a secret investigation that might have helped postmasters prove their innocence.

Separately, Business Secretary Kemi Badenoch has denied claims from former Post Office chair Henry Staunton that he was told to delay compensation payments to allow the government to "limp into the election".

BBC iPlayer - Panorama - The Post Office Scandal

This Panorama special tells the story of those whose lives were utterly devastated, reveals the damning evidence that was kept from them and investigates how and why the Post Office, a multinational tech company and the government covered up the truth for so long. (UK only)