A whistleblower from Fujitsu's Stevenage call centre has spoken out about the "horrendous" impact of the Post Office Horizon scandal.

Nate Orrow, who worked at the call centre between 2010 and 2012, told ITV News about his experiences answering calls from sub-postmasters.

He said: "It was difficult, talking to people where some of them were, as you can imagine, pretty desperate."

Wednesdays - accounting day for sub-postmasters - were Nate's busiest days, with the "bulk" of calls about the "accounting discrepancies" in the Horizon software that were used as evidence to prosecute more than 900 sub-postmasters.

Horizon was developed by Fujitsu, and has been used by the Post Office since 1999.

A High Court judge ruled in 2019 that Horizon was faulty, and the Post Office agreed to pay £58m to a group of sub-posmasters - though they only received £12m after legal costs were deducted.

Nate told ITV News that he "regularly" had upset sub-postmasters phoning in, and that the calls could come "back to back for hours" with "no respite".

"We all were leaving [on] Wednesdays feeling particularly stressed, and I do remember coming home and talking about it, and just how bad things were."

He said that he and his colleagues knew "it was a bad piece of software" and that they "hated supporting it".

But, he added, he and his colleagues would have been "dragged over the coals" if they had "ever made any kind of suggestion" that Horizon was not working as intended.

And, while Nate is not at fault for any of the scandal, he said: "It's difficult not to feel a level of second-hand guilt, because it's not my fault that it happened, but some of the information that I logged on to the system could have been used to prosecute, and that feels horrendous.

"I look back now, and I genuinely wish I hadn't worked there."

The ITV News bulletin, broadcast yesterday evening (Thursday, February 1), showed one former sub-postmaster who was brought to tears after watching Nate's interview.

Harjinder Butoy, who was sentenced to three years in prison after the Post Office accused him of stealing £200,000, criticised Fujitsu and Post Office management, saying that it was "absolutely shocking" and "wrong", and that they had made sub-postmasters "look like thick idiots".

"People said we never asked for help - everyone was crying out for help from the help desk."

The Horizon scandal recently returned to the forefront of public attention after ITV broadcast the Mr Bates vs The Post Office drama series.

To date, only 95 sub-postmasters have had their convictions overturned. A public inquiry began in February 2021 and is ongoing.

Responding to ITV's story, a spokesperson for Fujitsu said: "The Fujitsu Group regards this matter with the utmost seriousness and offers its deepest apologies to the sub-postmasters and their families.

"The UK statutory public inquiry, to which our UK subsidiary is providing full cooperation, is examining complex events that have unfolded over many years, and we remain steadfast in our commitment to this cooperation.

"Based on the findings of the inquiry, we will also be working with the UK government on the appropriate actions, including contribution to compensation.

"The Fujitsu Group hopes for a swift resolution that ensures a just outcome for the victims."