Former Post Office boss Paula Vennells has broken her almost decade-long silence on the Horizon scandal as she was quizzed on how things unfolded on her watch.

During her evidence to the Post Office Horizon IT Inquiry, Ms Vennells cut an emotional figure as she broke down twice under questioning from counsel to the inquiry Jason Beer KC.

Here, the PA news agency looks at what we have learned from her first day of evidence:

– Vennells admits false statement to MPs

In an exchange that prompted her to reach for a tissue and compose herself, the former chief executive admitted she had made a false statement to parliamentarians, but unintentionally.

She had told MPs the Post Office had been successful in every case against subpostmasters in court.

After Mr Beer listed a number of cases in which the business had not been successful, Ms Vennells said: “The Post Office knew that and I completely accepted.

“Personally I didn’t know that and I’m incredibly sorry that it happened to those people and to so many others.”

– Vennells faced accusations of knowing about IT errors from ex-Royal Mail chief

On a day where subpostmasters accused the former Post Office boss of a “cover-up”, the probe heard the ordained priest was accused of knowing about Horizon bugs by ex-Royal Mail Group chief executive Dame Moya Greene.

Dame Moya told her “I can’t now support you” after telling Ms Vennells: “I don’t know what to say. I think you knew.”

Ms Vennells then said: “No Moya, that isn’t the case.”

Dame Moya replied: “I want to believe you. I asked you twice. I suggested you get an independent review reporting to you. I was afraid you were being lied to.”

– Vennells ‘made mistakes’ but denied conspiracy

The 65-year-old apologised multiple times during her evidence while addressing a variety of topics, but maintained that there was no conspiracy at the Post Office during the scandal.

Ms Vennells said it was her “deep sorrow” that people, including herself, had “made mistakes” and “didn’t see things, didn’t hear things”.

But she told Mr Beer: “I have no sense that there was any conspiracy at all.

“I may be wrong but that wasn’t the impression that I had at the time. I have more questions now but a conspiracy feels too far-fetched.”

– Vennells unaware of extent of Post Office prosecution function for several years

Ms Vennells said she did not know the extent of the Post Office’s criminal investigations and private prosecutions until 2012.

She told the probe she was “very sorry” she did not “understand the extent” of the company’s prosecutorial function.

Asked why senior staff did not know this, Ms Vennells said: “It’s completely unacceptable that that was the case and that people, including myself, didn’t know.

“My only explanation for that is that it had been going on for so long, that it was an accepted reality, it was the status quo that I joined and accepted, I shouldn’t have done.”

– Horizon was like ‘Fort Knox’

Fujitsu Europe’s then-chief executive Duncan Tait described the core of Horizon like “Fort Knox” or an “aircraft flight recorder” when discussing remote access, Ms Vennells said in her first witness statement.

Ms Vennells and Mr Tait concurred it was “implausible” that Post Office branch accounts could be altered remotely.

The statement read: “Duncan described the core of Horizon like a black box, ie., similar to an aircraft flight recorder; he said that even if someone wanted to, it was not possible to alter or break it.

“I had heard the black box description before. He described how secure the system was – that even if someone had the motivation, it just wasn’t possible – Horizon was like Fort Knox.”