Gwyneth Hughes, the writer of Mr Bates vs The Post Office, said she was warned ahead of its release that “probably not many people would watch it”.

The ITV drama about the Post Office scandal has instead had an “unbelievable” response, she said.

Gwyneth Hughes told Sky News programme Sunday Morning With Trevor Phillips: “We’ve all been blown away by it.

“On the eve of transmission our boss sent us all (a) comforting email warning us that (it) probably wouldn’t do that well, and probably not many people would watch it, but, never mind, it will find an audience, which is television speak for nobody is ever going to watch it.

“So we woke up (the) next morning, and he literally thought that he had misheard the ratings, and it just has got bigger and bigger.

“The whole thing is unbelievable, the story of the postmasters, and what happened to them was completely unbelievable from beginning to end and this is, I think, just the (latest) unbelievable chapter in the unfolding, ongoing story.”

Since its release, Mr Bates vs The Post Office, which began on January 1 and stars Toby Jones, has led to the Government speeding up its response to help subpostmasters who were victims of a miscarriage of justice.

Ms Hughes said the emails, transcripts and interviews of former chief executive Paula Vennells were used to depict her as “nobody at the Post Office hierarchy wanted to get involved”.

Ms Vennells has since announced that she will hand back her CBE and Prime Minister Rishi Sunak has said hundreds of the wrongly prosecuted Post Office managers in England and Wales could have their names cleared by the end of the year under blanket legislation.

Ms Hughes, who is also a documentary-maker, said even the best documentaries “sort of appeal to your head rather than to your heart”.

She added: “It’s always someone sitting there telling you something terrible that happened to them in the past, whereas in drama, you’re right there during this terrible event, experiencing it through the eyes of the person who went through it, and, in the hands of a brilliant actor, that just can grab your heart and grab your attention like nothing else.”

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This has been “the most extraordinary couple of weeks” for Ms Hughes so she currently has no plans for the future.

She added: “The inbox is full of people saying to me ‘I’ve got a story for you, it’s even worse than the Post Office’ so, yeah, I (will stay) in a darkened room then think of something else.”

What was the Post Office scandal?

The Horizon IT scandal saw more than 700 subpostmasters and subpostmistresses handed criminal convictions after faulty Fujitsu accounting software made it appear as though money was missing at their branches.

Following the airing of the TV drama, more Post Office managers have come forward.