Gareth Jenkins: The Horizon architect under the spotlight

From 2005, Mr Jenkins was pivotal in helping the Post Office defend its faulty computer software system in criminal and civil cases.

“He was the ‘go to’ Fujitsu expert on any question of its reliability,” says David Enright.

In 2010, Mr Jenkins gave evidence in the trial of Seema Misra at Guildford Crown Court.

She told the BBC: “I was naïve at that time. I thought it was a good thing that he was working for Fujitsu because he would know the system inside out.

“If anything was going wrong in Horizon, he would have seen it.”

What Mrs Misra did not know was that shortly before the trial, Mr Jenkins had flagged a bug that affected dozens of branch accounts, and that he had suggested remotely accessing their computer terminals as one way of fixing the problem.

Mr Jenkins did not disclose this in court. Mrs Misra was found guilty of theft and false accounting and was sent to prison whilst pregnant.

If the problems had been revealed at the time, it could have stopped all the prosecutions in their tracks.

Two years later, solicitors acting for sub-postmaster Kim Wylie asked about remote access. Mr Jenkins sought guidance on what to say, warning a Post Office lawyer that including this possibility could lead to more scrutiny.

His final witness statement confirmed that this could happen, and he went on to say in his final version that altering branch accounts in this way was rare and needed to be authorised by the Post Office.