Stein is now drawing attention back to a document that outlines monthly recovery amounts to the Post Office from legal prosecutions.

Stein quotes the report, outlining how the Post Office was dealing with 248 investigations worth an excess of £9m before highlighting a part that says 80 were going through the courts.

"You had all of the information that was possible to have to actually have governance of this area," says Stein.

Cook replies meekly by saying, "again, I've said I could've done more".

The information you were getting was "quite comprehensive" regarding the ongoing investigations under your time at the Post Office, Stein asks Cook.

"It was, but I don't wish to let the impression be created that this was there to chase sub-postmasters, this was to chase fraud in general."

James Gregory
Reporting from the inquiry

A very heated exchange here between Alan Cook and Sam Stein KC, from Howe and Co law firm, which is representing a large number of sub-postmasters and sub-postmistresses.

Stein gets Cook to repeat that he only fully understood years into his tenure at the Post Office that he was running a prosecuting authority.

He then asks a question that draws a smattering of laughs around the room: "What do you think the criminal law team did in the Post Office or Royal Mail?"

"Involved with prosecutions," Cook answers, before adding he did not know this was in relation to sub-postmasters, and this was "there to chase fraud in general".

Stein accuses Cook of lying in his witness statement when he wrote that he was not aware prosecutions were taking place in the Post Office's name.

Image source, EPA

Sub-postmasters and sub-postmistresses are managers at Post Offices across the UK. They take responsibility for the everyday running of a Post Office, including the money going in and out of the business.

They handle people’s savings and pensions, and are often at the heart of their communities.

Between 1999 and 2015, the Post Office prosecuted 700 sub-postmasters and sub-postmistresses - an average of one a week - based on information from a faulty computer system called Horizon.

Some 283 other cases were brought by bodies including the Crown Prosecution Service.

Postmasters and postmistresses were jailed, went bankrupt, saw their marriages destroyed, and some died before their names were cleared.

We’re being shown more email exchanges from October 2009, which were prompted by Michael Rudkin’s earlier warning that the press were starting to get interested in Horizon.

In the emails, Cook described the Horizon problem as an “escalating and serious challenge”, noting a new version of the programme was due to be rolled out in a few months.

He also said they should be “careful” about asking for more information without first talking to Paula Vennells, a former Post Office CEO.

Cook tells the inquiry he’s not sure in hindsight why Vennells needed to be informed and says he doesn’t remember discussing it with her at that time.

Image source, Post Office Inquiry

Cook is asked more about what he thought the outcome of the investigation would be.

He says he thought it would find things that were not the fault of people running the Post Offices, saying it didn't necessarily have to be the technology and could have been the procedures.

He says he has "difficulty in remembering" the outcome of the review and he thinks it went beyond the time when he left the role.

Correspondence is now being shown to the inquiry that shows another email from October 2009 that discusses conference calls with another former Post Office boss, David Smith.

In an email detailing conference calls between the two, Alan Cook is quoted as saying that he is asking "for more robust defence of Horizon".

Cook maintains that those were not the words he would have used at the time, and concedes that "one of the perils of being the boss is that people use your name to get things done".

He says had he been copied into that email correspondence, he would have responded but he was not.

"Robust" was a word I used at the time, Cook says, but "defence", he says, is not a word he would have used to describe his work looking into Horizon.

Cook is being pressed on what he did to ensure a proper investigation into Horizon got off the ground.

He says he pushed for an investigation and wanted to know who would run it. He thought a “no nonsense, knowledgeable guy” was in charge who would give an honest opinion.

One of the problems, Cook says, is that individual cases against sub-postmasters were still being investigated rather than the “whole thing”.

He continues: "I didn’t know what the problem was but it was clearly wider than the cases that had been highlighted to me."

Questions about the aforementioned Computer Weekly article persist.

Inquiry lawyer Stevens says Cook, who was in charge of the Post Office between 2006 and 2010, received a body of complaints from MPs after the article and asks why - if Cook saw it as escalating and significant - he did not arrange an independent investigation at this point.

Cook says the first step seemed to be to investigate it "ourselves" and "ask ourselves what could be wrong".

James Gregory
Reporting from the inquiry

An email is now being shown from Mary Fagan, a Post Office PR officer, dated from 2009 that flags to Cook how there is steadily building "nervousness" around the Horizon system.

Cook's reply is brought up on the screens next. In it, he expresses scepticism over reports the system was to blame for shortfalls: "My instincts tell that, in a recession, subbies with their hand in the till choose to blame the technology when they are found to be short of cash".

Cook looks mildly embarrassed as it is put to him at the inquiry and says it is an "expression I'll regret for the rest of my life".

He says it is an "inappropriate thing to put in an email".

There is also a rare intervention from inquiry chair Sir Wyn Williams who asks him whether this was indeed his sentiment about the sub-postmasters.

Cook says the sentiment was expressed but the words in his email were "unacceptable".

Cook is being asked about what discussions were taking place in October 2009 after the Computer Weekly article was published.

In one email, he is warned the press are “digging the dirt” on emerging allegations about the accuracy of Horizon.

That warning came from Michael Rudkin, who worked for the union representing sub-postmasters. He has since campaigned for justice for those convicted, which includes his wife.

It's put to Cook that Lee Castleton's trial was going on while he was managing director.

Stevens says the legal costs in pursuing the claim were "significant", prompting Cook to clarify that he might not have known the case or the individual involved, but there was reporting he would have seen on the costs of legal spending.

Challenged over why he did not think to ask why there was such a significant legal cost on one case, Cook says he cannot recall, but says either it was a mistake on his part or it wasn't in the report he was given.

The Computer Weekly article, external from May 2009 is now being pulled up, which as we just mentioned former Post Office boss Alan Cook says he saw before the aforementioned February 2009 letter to an MP.

Inquiry lawyer Sam Stevens draws attention to the specific case of Lee Castleton, a sub-postmaster who was found to have a 25,000 shortfall at his branch after being sued by the Post Office.

Stevens presses Cook about whether he knew about Castleton's specific case before the May 2009 article was released, to which he says "no".

Now we're being shown a February 2009 email from Rebecca Thompson, the journalist who was the first to cover the case of sub-postmasters in Computer Weekly, to an MP who sat on the business select committee.

The letter had been forwarded to Cook by Pat McFadden, then a business minister. It sets out a broad outline of what is now referred to as the Horizon IT scandal.

Asked if he remembers seeing this letter, Cook says "this was the moment" and tells the inquiry he happens to have seen the Computer Weekly report shortly beforehand.

Cook tells the inquiry he was concerned enough to ask for a thorough investigation into the matter.

Alan Cook, an ex-Post Office managing director, is asked if he did anything else to get more feedback about Horizon IT system, besides the visits to around 250 branches.

Cooks says that his primary focus was on the National Federation of SubPostmasters, which he says he used as the mouthpiece of sub-postmasters.

The organisation represents sub-postmasters around the UK.

James Gregory
Reporting from the inquiry

At times this morning I have heard some groans from around the room - presumably from affected sub-postmasters, sub-postmistresses and their families - during Cook's testimony.

One man sat near me sighed loudly when the former managing director told the inquiry earlier he could not recall certain Post Office documentation.

Cook is talking about how one of his early objectives in his role was to meet members of the sub-postmasters community who he said he believed felt "unloved to a degree by Post Office Ltd".

He talks of a "programme of visits" to branches around the country, where he received "plenty of feedback" from sub-postmasters, and about his close relationship with the federation which represented the community.

Cook is then asked more details from his statement where he says he visited 250 branches over a few years, which Stevens acknowledges would have been a small fraction of Horizon users.

Cook pushes back by saying that no matter what way you slice it, "all the numbers in the Post Office were very large" and that you still "do what you can do".

He adds that he always found these visits "illuminating".

Next Cook is asked whether anyone on the board was spending time thinking about whether Horizon reliability could impact sub-postmasters.

He says that when he joined the Post Office, he felt "the sub-postmaster community felt unloved" and that he tried to "get close" to those branch managers.

Cook would spend Fridays visiting hundreds of branches around the country, he tells the inquiry, in order to get feedback from sub-postmasters and "keep my feet on the ground".

Cook is now asked if he felt able to challenge the Post Office executive board.

He says he felt comfortable to challenge to a level that was comparable with his experience, but says he was not purporting to be an expert in every functional activity.

He is asked if at any point he asked for more IT support in order to better challenge the executive, and Cook says: "There wasn't an appetite to have other non-execs on the Post Office Ltd board, and we did have the group IT director sitting on the Royal Mail Holdings board."

He adds: "These things were going up to the Royal Mail Holdings board and there was more challenge available there".

Image source, Post Office Inquiry

Now the inquiry is looking at emails sent in 2006 from Fujitsu employees, which outlined the issue of a Horizon IT bug called "the Riposte Lock."

Stevens reads out from the emails how "a number of sites" had been impacted and asks whether Cook views this as a significant concern.

Cook replies by saying that he's unsure if the problem being outlined in the emails is the same as other discrepancies.

High number of Horizon convictions during Cook's tenurepublished at 11:12 British Summer Time 12 April

11:12 BST 12 April

Ben King
Business reporter

Alan Cook was appointed managing director of the Post Office in March 2006, and left in March 2010.

According to evidence submitted to the Horizon Inquiry by Simon Recaldin, Director of the Post Office's remediation unit, these years saw some of the highest numbers of convictions using Horizon evidence.

The Post Office secured 292 Horizon convictions from 2006 to 2010 in England and Wales, most of which overlapped with Cook's time at the top.