SCOTT SIMON, HOST:

A story about a British postal scandal has been making international headlines. Hundreds of postal workers were wrongly prosecuted between 1999 and 2015. The story has come to light because of a new TV drama that just aired in the U.K. "Mr. Bates Vs. The Post Office" stars Toby Jones and details how postal workers were accused of stealing money when computer software called Horizon was to blame.

(SOUNDBITE OF TV SHOW, "MR BATES VS THE POST OFFICE")

UNIDENTIFIED ACTOR #1: (As character) The computer system the Post Office spent an arm and a leg on is faulty.

UNIDENTIFIED ACTOR #2: (As character) No one else has ever reported any problems with Horizon. No one.

UNIDENTIFIED ACTOR #3: (As character) You're responsible for the loss.

UNIDENTIFIED ACTOR #4: (As character) I haven't got that money, and I don't know where it's gone.

SIMON: TV show and the true plight of the postal workers has caused outrage among the British public and political backlash. Lee Castleton is a former Post Office manager. Nick Wallis is an investigative journalist who wrote the book "The Great Post Office Scandal." Gentlemen, thank you both for being with us.

NICK WALLIS: Thanks for having us.

LEE CASTLETON: Hi.

SIMON: Mr. Castleton, what's it been like to see your story and those of others on a hit TV show?

CASTLETON: It's very, very odd. It's very humbling. And it kind of reinvigorates you in enthusiasm to get to the end of this and just enjoying the moment, really, and trying to put everything into the right place.

SIMON: Mr. Wallis, I gather one of the reasons the scandal has hit the British public so hard is, of course, firstly, a great many people were wronged. And also the Post Office has been a pretty trusted institution, hasn't it?

WALLIS: Absolutely. And that's why so many subpostmasters went into business with the Post Office. They opened a retail premises. They agreed to allow a Post Office counter to be installed in their premises, and they thought they were dealing with a fair and equitable partner that had been around for centuries and who would treat them fairly. They had responsibility for handling public money. But when this horrendous IT system was rolled out, which literally could not add up properly - we've discovered this from the public inquiry that's been going on; the cash accounting program was fundamentally broken - it created holes in subpostmasters' accounts, and instead of properly investigating that IT, the Post Office decided to use its investigatory and prosecutorial powers to take innocent people to court. And hundreds of people, innocent people, were given criminal convictions as a result of the Post Office relying on faulty IT evidence.

SIMON: Mr. Castleton, you were accused of stealing money from the Post Office, which was not the case. What did you and your family go through?

CASTLETON: Oh, it's probably the most terrible journeys that anyone could take. And the victims throughout, all the victims, the story is so similar. The Post Office were just not interested in the human side - took me to bankruptcy. We lost everything. And my wife suffered from anxiety that led to epilepsy, and my daughter terribly suffered. She was bullied as well as my son. They were both bullied at school, which led to my daughter being very anxious and eventually an eating disorder which took 10 years for her to start to recover from. And this has been 20 years for me.

SIMON: What did people say when you said, but I'm innocent?

CASTLETON: People would say that I was a thief, that they'd been told by the Post Office. Everyone trusted the Post Office. It's owned by the government. And people would say that I'd taken pensions from old people.

SIMON: Mr. Wallis, why did it take so long for the Post Office to discover the problem and recognize they were at fault?

WALLIS: The Post Office didn't discover the problem. The Post Office went into denial mode to a terrifying degree. When it became apparent in 2013 to the board-level members of the executive team that it may have been responsible for using faulty evidence to put innocent people in prison, rather than raising their hands and telling Parliament and telling the campaign groups, which had been springing up over the course of the previous decade, they decided to hide that evidence, and successive executives denied publicly to the media and to Parliament that they had been responsible for any miscarriages of justice.

And it wasn't until Lee, the lead campaigner, Alan Bates, and many hundreds more banded together to get litigation funding to take on the Post Office at the High Court that it was forced by a High Court judge after an extremely aggressive litigation in which the Post Office attempted to remove the judge when they didn't like the way that he was thinking on this subject. The Post Office caved, settled and handed over millions of pounds in compensation.

SIMON: There are some people who went to prison. There are some people who didn't survive, aren't there?

WALLIS: More than 200 people were given custodial sentences. More than 900 people were given criminal convictions. There were people who told me that they thought, in their darkest moment, of taking their own lives, as if it would be less painful and an easier thing to do than have to wake up and face their communities every day with this cloud of suspicion, and their families as well. Families were broken apart. We know of four confirmed suicides. But these subpostmasters who've been struggling to get their stories heard have now got the world's media wanting to talk to them, and they have done everything possible to keep going, to agree to every single interview opportunity that comes their way just so they can keep hammering the story, going to the well one more time, retraumatizing themselves in order to be able to talk about what happened to them in the hope they might get justice.

SIMON: Mr. Castleton, Prime Minister Sunak says he wants to make this right. What would that be for you?

CASTLETON: Well, the original case in the High Court, it still stands against me. That would be the first step. And then we need to look at all the convictions to be removed and then move on to compensation. Everyone needs to be fully and fairly compensated. And then finally accountability - you know, this is a company that's wholly owned by the government, and there's never been anyone removed from their employment. There's never been anybody taken to court, prosecuted or ever punished. And in order to draw a line under all of this, we need those steps to take place. Otherwise you just don't get closure.

SIMON: For all you've been through, what would you like us to know? What would you like us to bear in mind?

CASTLETON: Oh, gosh, the humanity of it, really. Nobody should have to fight this hard. The group have pulled up every single tree. They fought every corner with no money, with nothing but just belief in justice. It's had terrible effects throughout families. You know, I equate it to holding a dry handful of sand and just watching every grain fall between your fingers. And you have no power, no power to stop it - just nothing. And I just wish that people would realize that should never happen to anybody.

SIMON: Lee Castleton managed a Post Office in the town of Bridlington. Nick Wallis is an investigative journalist. Thank you both very much for being with us.

WALLIS: Thank you.

CASTLETON: Thank you. Transcript provided by NPR, Copyright NPR.