One of Britain's biggest miscarriages of justice, the wrongful conviction of hundreds of Post Office workersdue to faulty software, has exploded into the public domain following a TV drama, triggering demands for justice.

In a more than 20-year scandal, some postal workers were sent to prison and others lost their livelihoods and homes.

An independent inquiry as well as a police investigation into the scandal are being carried out, and business executives and former ministers are under scrutiny.

Below is a detailed look at the case:

WHAT IS THE POST OFFICE SCANDAL?

Hundreds of self-employed workers at the state-owned Post Office were wrongly prosecuted or convicted between 1999 and 2015 for false accounting, theft and fraud, because of a glitches in a software system that incorrectly showed money missing from accounts.

Some spent time in jail while others went bankrupt, saw their marriages destroyed and some died before their names were cleared.

Managers at Post Office branches across Britain, called sub-postmasters, are often at the heart of their communities, trusted individuals who handle people's savings and pensions.

The Post Office maintained for years that data from the defective Horizon computer accounting system, developed by Japan's Fujitsu and rolled out in 1999, was reliable, while accusing sub-postmasters of theft.

HOW DID THE SCANDAL UNFOLD?

The issues with Horizon, where the system would incorrectly show shortfalls in the accounts of individual branches, began to be reported to the Post Office from the early 2000s.

Over the next decade, a number of sub-postmasters either found their Post Office contracts terminated, were made bankrupt or were jailed after being found guilty of stealing money.

In 2009, trade publication Computer Weekly reported the claims of flaws with Horizon, alongside the postmaster prosecutions.

Amid mounting pressure from the media and lawmakers, the Post Office began to investigate the issue, but in 2015, its boss Paula Vennells told a parliamentary committee that there had been no evidence of any miscarriage of justice.

WHAT COMPENSATION HAVE VICTIMS RECEIVED?

In late 2019, the Post Office agreed to settle claims made by 555 sub-postmasters. However, many of the victims found the amount paid in compensation was outweighed by legal fees.

The government says roughly 138 million pounds ($175 million) have so far been paid out to over 2,700 claimants across three separate Post Office compensation schemes.

Still, many postmasters are yet to receive compensation or have their convictions quashed.

WHAT IS THE GOVERNMENT DOING?

Spurred to act following a public outcry after the TV drama, Prime Minister Rishi Sunak is seeking to use new legislation to overturn the wrongful convictions, calling it one of the greatest miscarriages of justice in Britain's history.

Under the plan, sub-postmasters will be able to sign a document to have their convictions reversed and claim compensation.

But some legal experts have warned that the unprecedented step of legislating to quash convictions meant that politicians were meddling in the independent judicial process, potentially risking similar interference in the future on other issues.

The normal process for anyone to have their conviction overturned in Britain is for the convicted party to lodge an appeal.

WHAT HAPPENS NEXT?

An independent public inquiry led by a former high court judge is gathering evidence from postal workers, the government, the Post Office, Fujitsu and others. The inquiry is expected to conclude later this year.

London's Metropolitan Police has also confirmed it is conducting its own investigation into the Post Office over potential fraud offences arising from the wrongful prosecutions.

HAS ANYONE BEEN HELD ACCOUNTABLE?

No senior Post Office staff have been punished to date.

Vennells, who received more than 4.5 million pounds in salary and bonuses during her seven-year tenure, stepped down in 2019 before the Post Office agreed to pay 58 million pounds in a settlement with 555 sub-postmasters.

In 2021 she resigned from the boards of two retailers after 39 sub-postmasters had their criminal convictions overturned, saying her past at the Post Office had become a distraction.

After a public outcry, Vennells returned her CBE, an honour bestowed in 2019 for services to the Post Office and charity, since the broadcast of "Mr Bates vs The Post Office", the ITV drama about the scandal.

Former postal affairs minister Ed Davey has also come under the spotlight. The now-leader of the small Liberal Democrats party refused to meet sub-postmaster Alan Bates in May 2010, saying in a letter that it would not serve any useful purpose.

Davey, who later met Bates but did not intervene in any of the cases, said he was "clearly misled" by Post Office executives.

Fujitsu, which has continued to win multiple British government contracts, says it is "fully committed" to supporting an ongoing independent public inquiry. It says it has apologised for its role in a scandal.

(Reporting by Sachin Ravikumar; Additional reporting by Alistair Smout and Paul Sandle; Editing by Paul Sandle, Ros Russell and Angus MacSwan)