Lawyer Sam Stevens is now asking Allan Leighton what he was told about the Horizon IT system during a meeting held in 2001, where he is listed as a non-executive director in the attendance list.

Leighton says that at the time he was told about the size and scale of the programme.

Leighton says he cannot recall any issues with Horizon being mentioned during the meeting that took place as soon as he joined the company.

When pressed, he says any issues raised with Horizon were about processes rather than any suggestion that the accounting data raised by the IT system was unreliable.

Allan Leighton begins by saying what happened was terrible for everyone involved, especially the sub-postmasters and mistresses, and he is sorry for "the elements of that" which occurred during his tenure at Royal Mail.

Allan Leighton, a businessman, has held several senior roles at the Post Office.

Leighton, 71, was once the chair of Royal Mail Holdings, and he was also the chair and non-executive director of the Post Office. He is also the former non-executive director of the Royal Mail Group.

Leighton was affiliated to the Royal Mail between 2001 and 2009, and to the Post Office between 2002 and 2009, according to Companies House records, external.

He was the Royal Mail’s chairman when some of the cases wrongly prosecuting sub-postmasters, because of incorrect information from the Horizon IT system, were brought to court. In the 1990s Leighton was Asda’s top boss.

Ben Hatton
Reporting from the inquiry

Former Royal Mail chairman Allan Leighton is being sworn in now.

He’s a well-known figure in the business world, having also been CEO of Asda, and he’s currently chairman of Pizza Express.

Unlike Longman, he's here in person.

Longman is now being asked about the case of Jennifer O'Dell. He is asked why he was considering a possibility of an allegation of false accounting, as shown in the evidence presented.

"There was still close to £10,000 missing," Longman answers but says that he should have marked it as "no further action".

Given that at the time he had believed there was something wrong with the case, "How on earth does that make sense?" he is asked again.

"All I can say is that there was an amount of money that was missing..." he says, and admits that he accepts the point: "There should have been no further action and that line should have not been in there."

That's the end for Longman in today's session of the inquiry.

Longman is asked whether issues with the Horizon IT system were "swept under the carpet".

"With hindsight I should have been more forceful," Longman replies.

Seema Misra's lawyer, who is sitting next to Misra in the inquiry, says Longman and his colleagues did not wish to investigate anything that might undermine Horizon.

To which Longman says that, looking back, more work should have been done where "unexplained losses had occurred". He adds that it wasn't part of their thinking at the time.

He is then told there was "institutional bias to do precisely the opposite" of what should have been done.

"Yes, I can't disagree," Longman tells the inquiry.

The inquiry hears that Seema Misra made numerous calls to the Fujitsu helpline when she discovered a problems with the IT system but the details of these calls were not fully shown to the court when she was prosecuted.

Longman is being asked about this. Why were the call logs not shown?

"You don't appear to be accepting responsibility," the lawyer tells Longman, for this and other criticisms of the way the case was handled.

Longman says he apologises.

"With hindsight maybe I should have been more forceful getting this disclosure to the defence," he adds.

Longman is now being questioned by a lawyer for Seema Misra, a former sub-postmistress who was wrongly jailed while she was pregnant.

He is asked whether there was good communication between himself and other investigators at the security department and the criminal law team.

Longman responds that as a national team, "I wouldn't say there was good communication".

We're now hearing more questions from the counsel towards Jon Longman. After the lunch break he is shown an email exchange that was forwarded to him back in February 2010.

The former Post Office investigator is asked whether he recalls an email chain where possible problems with the Horizon IT system's transaction logs were flagged.

Longman says he agrees that the email suggests there were problems, but he is not sure if the email relates directly to the question in a previous statement.

He is pressed further but cannot recall if there were discussions resulting from the issues flagged in that email.

Ben Hatton
Reporting from the inquiry

One former sub-postmaster, Christopher Head, who was himself pursued in the courts by the Post Office, is here today listening to the evidence.

“I just think it’s that thing again that they believed what they were told,” he tells me during the break.

“It’s that groupthink, maybe institutional bias - they didn’t want to delve and ask the right questions to understand exactly what was going on.”

The inquiry is back from its lunch break.

Before we move on to Allan Leighton, who held several senior roles at the Post Office, there will be a few more questions to Post Office investigator Jon Longman.

We'll soon be hearing from Allan Leighton. He is a businessman who has held several roles with the Post Office and the Royal Mail.

Leighton, 71, was once the chair of Royal Mail Holdings, and he was also the chair and non-executive director of the Post Office. He is also the former non-executive director of the Royal Mail Group.

Leighton was affiliated to the Royal Mail between 2001 and 2009, and to the Post Office between 2002 and 2009, according to Companies House records, external.

He was the Royal Mail’s chairman when some of the cases wrongly prosecuting sub-postmasters, because of incorrect information from the Horizon IT system, were brought to court. In the 1990s Leighton was Asda’s top boss.

If you've just joined our coverage of today's Post Office inquiry hearing, here's a round-up of what's happened so far:

• Former Post Office investigator Jon Longman has been giving evidence today at the hearing
• He investigated sub-postmasters until 2012, including Seema Misra who was wrongfully jailed while pregnant after being accused of stealing £74,000
• Longman said he "was always told Horizon was robust" and so he did not have concerns about the growing number of challenges
• He admitted he was "never comfortable" with the case of sub-postmistress Jennifer O'Dell who was wrongly accused of stealing more than £9,600 in 2009, adding the system should have been investigated
• Post Office investigators feared a "world of trouble" if the organisation lost a case based on Horizon's integrity, internal emails showed

Azadeh Moshiri
Reporting from outside the inquiry

I caught up with David Enright, whose firm represents former sub-postmasters. His own clients include Jennifer O'Dell, whose case is one Jon Longman has said he had "reservations" about.

In a write-up of an interview with O'Dell shown at the hearing, Longman wrote she blamed losses on Horizon and refused to make good the audit shortage. Yet, at the time, Longman did not think it was relevant to disclose the challenge to the Horizon IT system in her case to Seema Misra's legal team.

Enright tells me his clients have accused the Post Office’s investigators of intimidation, bullying, and acting like "heavies" who were "demanding to know where the money has gone".

"Of course, we now know that money simply didn’t exist, it was a phantom fantasy of a broken computer system," he adds.

He says this is at the heart of what this inquiry is trying to do – to demonstrate “the way these people were treated was wrong”.

Longman wrote a letter that requests costing information "as soon as possible from Fujitsu", saying that the information from the lawyers dealing with the Horizon integrity issues was getting very large.

The letter was written after a meeting with the solicitors from different branches.

After reading that letter, Blake asks if he thought the costs were getting too much.

"It wasn't my comment, that was what was said by the solicitor at the meeting," Longman answers and adds:

"I didn't go there and say it's very costly you should challenge it, it came out from the meeting with the solicitors. I had no involvement with that."

The inquiry is now taking a break for lunch.

We'll catch you up on a few more lines that we heard before the break, so stick with us.

The hearing is shown an email chain in which a Post Office lawyer says it expects to get more claims from sub-postmasters challenging Horizon's integrity and "this has been building a head of steam for years".

Longman is asked during the hearing if he agrees with that sentiment. He says: "Yes I think they'd been increasing."

Another email is shown to the hearing in which a Post Office lawyer writes Longman is saving them "hundreds of thousands" in external fees and asks for him to be freed up.

Longman tells the hearing he was helping the Post Office deal with disclosure requests.

The inquiry is shown a well-known email, which has been shown a number of times during the inquiry. It is from October 2010 from Jarnail Singh, a senior Post Office lawyer, congratulating people on the success in the Seema Misra case.

Blake reads the part saying "it is to be hoped the case would set a marker to dissuade other defendants from jumping on the Horizon bashing bandwagon" and asks if Longman shares this view.

"Not at all," Longman says. "I don't know why that comment was put in, it wasn't necessary, I didn't respond to that email," he adds, saying that he remembers clearly.

"Did you think the Misra case was significant in relation to dissuading other defendants from challenging Horizon?" Blake asks.

"No, I don't think it was dissuading. But there were a lot of people in different departments of the Post Office watching the outcome of this very closely so it developed into a bit of a a test case I suppose," Longman answers.

Ben Hatton
Live reporter

A reminder, Misra is sitting here in the inquiry room listening to this evidence about how her case was handled by the Post Office - a case that led to her wrongful conviction.

It’s hard to tell from where I’m sitting, but where I can catch her expression, she seems unfazed, and just listening intently.

An email is shown to the hearing from Andrew Daley, security programme manager at the post office in July 2010.

Longman is asked in the email if he was aware of Post Office executives' concerns about Horizon, with Daley adding "we'll be in a world of trouble' if a case was lost based on the system's integrity.

Longman is asked during the hearing if he was aware of any concerns from Post Office executives over Horizon. "No," he tells the hearing.