A former senior Fujitsu engineer has denied hiding problems with Horizon during a trial which led to a wrongly convicted pregnant subpostmaster being jailed, the Post Office Horizon IT Inquiry heard.

Gareth Jenkins also told the inquiry on Friday he believes the issues are “down to the way (the) Post Office has behaved”.

Mr Jenkins worked at Fujitsu, formerly known as International Computer Limited, for the whole of his professional career before retiring in 2015, and had been a “distinguished engineer” since the mid-1990s.

His evidence about the Horizon system was used in the prosecutions of many subpostmasters, including Seema Misra, who was given a 15-month prison sentence in November 2010, when she was eight weeks pregnant.

Previous witnesses to the inquiry have claimed Mr Jenkins may have committed perjury due to his failure to disclose knowledge of bugs in the Horizon system to the subpostmasters.

He is currently the subject of a Metropolitan Police investigation on suspicion of perjury and perverting the course of justice.

Flora Page, representing a number of subpostmasters, described Horizon as an “out of control monster” by the time of Ms Misra’s trial and added that “hundreds of people had already had their lives ruined to protect it”.

She put it to Mr Jenkins: “Isn’t the truth that you knew Horizon was a monster and it was causing harm?”

He replied: “No, that’s not how I felt.”

Ms Page put to Mr Jenkins that he “threw mud in the jury’s eyes”, to which he said: “I did not.”

She put it to Mr Jenkins that failing to tell the court that he knew that transactions were being injected at the counter was failing to tell the whole truth.

He said: “I didn’t think that at the time.”

It was put to him that there were “thousands of known error log entries”, and Mr Jenkins said: “I’m not sure how many known error log entries there were, I don’t know the volumes.”

Ms Page said that during the trial Mr Jenkins was asked if he knew whether there were any problems with the Horizon system that Fujitsu was aware of, and put it to him that the truthful answer would have been “cash accounts, remote access, tampering, bad error handling, silent faults across the system, the EPOSS code, the terrible code, hardware failures, persistent hardware failures, recovering transactions that were lost”.

Mr Jenkins replied: “That was not how I understood the question to be.”

“You hid all these issues and problems when you gave evidence against Seema Misra, didn’t you?” Ms Page said.

He replied “no”, then later added: “I did not believe that I deliberately hid anything.”

An email chain from February 2011 was shown to the inquiry in which Mr Jenkins was asked if he had watched an Inside Out programme on subpostmasters being accused of false accounting.

Mr Jenkins replied to the email saying he had watched it, and he added: “I was pleased that Fujitsu wasn’t mentioned, POL (Post Office) have a significant problem!”

The former engineer told the inquiry: “My feeling was then and is now that the issues to do with this are down to the way Post Office has behaved rather than actual faults in the Horizon system and that I think is behind what I’ve said there.”

Ms Page put to Mr Jenkins that during his evidence in Ms Misra’s trial he told the judge that him “being a Fujitsu man had no impact” on his evidence.

Mr Jenkins replied: “I don’t believe that it did. I believe that I told the truth as I understood it at the time.”

“You were a Fujitsu man doing what Fujitsu needed you to do to protect the monster,” Ms Page put to him.

Mr Jenkins said: “I didn’t think it was a monster.”

During his evidence, Mr Jenkins said: “I am sorry what what happened to Ms Misra but I feel that was due to the way that Post Office had behaved and wasn’t purely down to me.

“I clearly got trapped into doing things I should not have done but that was not intentional on my part.”

Clair Dobbin KC, representing Mr Jenkins, raised a number of statements the former engineer gave during his evidence in Ms Misra’s trial.

Comments she mentioned included that there could be problems he was not aware of and him replying “no I don’t think so” when being asked if a computer system could be perfect.

She asked if Mr Jenkins agreed that a number of points made “might be thought that you gave evidence that wasn’t helpful to the prosecution case”, and he replied “indeed”.

On Thursday, Mr Jenkins said he “felt happy” at the time with evidence he gave as part of Ms Misra’s trial.

A transcript of parts of Ms Misra’s trial was shown to the inquiry on Thursday, and Mr Jenkins was questioned about his evidence, during which he said the Post Office’s help desk “wasn’t actually very good at passing things on when they should have been” and added he had not gone through Ms Misra’s call log with the help desk before giving evidence.

Asked by counsel to the inquiry Jason Beer KC if he was “untroubled by and happy with the evidence” he gave at Ms Misra’s trial, Mr Jenkins said: “At the time I was, I clearly appreciate now that it wasn’t as good as it should’ve been but at the time I felt happy with it.”

And earlier in the day Mr Jenkins was questioned over a series of emails he sent and apologised during his evidence twice.

He sent an email on March 1 2010 discussing the case of Ms Misra, which said she saw an article in Computer Weekly “indicating that Horizon was unreliable and she decided to jump on the bandwagon”.

Mr Jenkins apologised during the inquiry, saying “that’s totally inappropriate wording on my part, for which I apologise”.

Another email was shown to the inquiry in which Mr Jenkins commented on a report and said “this is another example of postmasters trying to get away with ‘Horizon has taken my money’”.

Mr Jenkins said: “That’s me very poorly trying to summarise what I thought was being laid out in the email trail below and I apologise for the wording that I used there.”

On Wednesday, Mr Jenkins admitted it was “inappropriate” for him to modify a draft witness statement to remove a reference to weaknesses in the Horizon system at the request of the Post Office.

A Post Office investigator had warned the company could be “embarrassed at court” if an acknowledgement of the software’s failures featured in the statement, which was requested in connection with allegations made against a subpostmaster in 2006.

Mr Jenkins also told the inquiry he thought any remote access would have been visible to subpostmasters and could be distinguished from changes made by third parties, although he acknowledged he knew it was “theoretically possible” this might not always be the case.

More than 700 subpostmasters were handed criminal convictions between 1999 and 2015 when errors in the Post Office’s Horizon IT system meant money appeared to be missing from many branch accounts when, in fact, it was not.

It has been branded the biggest miscarriage of justice in British legal history.

Mr Jenkins has given evidence for four consecutive days up to Friday, the longest run of questions any witness has faced so far.