Post Office investigators feared there would be a “world of trouble” if the company lost a court case based on Horizon failings, an inquiry has heard.

The Horizon IT inquiry was shown an email sent in July 2010 by Post Office security programme manager Andrew Daley to a number of staff saying Horizon issues were “still very much in the spotlight and not going away”.

The email was sent around the time of a case against pregnant subpostmistress Seema Misra, who was handed a 15-month prison sentence on her son’s 10th birthday in November 2010 after being accused of stealing £74,000.

She began running a Post Office in West Byfleet, Surrey, in 2005, but was suspended in 2008.

Former Post Office investigator John Longman told the probe Mrs Misra had turned into a “test case” for the business.

He said: “It developed… and I didn’t know this at the time, I think there was a lot of people in different departments within the Post Office watching the outcome very closely.

“So it developed into a bit of a test case, I suppose you could say.”

The inquiry was shown an email Mr Longman received from senior lawyer Jarnail Singh following Mrs Misra’s case, which said it was hoped the verdict would “dissuade other defendants from jumping on the Horizon bashing bandwagon”.

Counsel to the inquiry Julian Blake asked: “Was that a view that you shared at the time, that there was a Horizon bashing bandwagon?”

Mr Longman said: “No, not at all.

“I do recall this email – I had to read it twice… just to confirm what had been written.

“I’d have to say that I don’t know why that comment was put in – it wasn’t necessary and I didn’t respond to that email.

“I remember it clearly and I don’t see that there was a Horizon bashing bandwagon going on.”

The inquiry was previously shown Mr Daley’s email, which read:  “Have you guys heard anything from the PO executive on the Horizon integrity risk?

“The investigators are concerned that if we lose a case based on the Horizon integrity, we’ll be in a world of trouble.

“They have also been getting queries from solicitors during case briefings. So this is still very much in the spotlight and not going away.”

During Mrs Misra’s case, lawyers warned her defence team that the retrieval of transaction data relating to her case was “not a free service”.

A legal letter from Post Office criminal lawyer Phil Taylor to Ms Misra’s team warned the organisation would “not underwrite the cost” if the data was deemed irrelevant by counsel.

The probe was also shown internal emails between Post Office investigators which said lawyers representing subpostmasters making “lumpy” requests for audit data were made to “pay up” because cases tended to end up in guilty pleas and it was usually an attempt at “muddying the waters”.

The Post Office has come under fire since the broadcast of ITV drama Mr Bates vs The Post Office, which put the Horizon scandal under the spotlight.

More than 700 subpostmasters were prosecuted by the Government-owned organisation and handed criminal convictions between 1999 and 2015 as Fujitsu’s faulty Horizon system made it appear as though money was missing at their branches.

Hundreds of subpostmasters are awaiting compensation despite the Government announcing that those who have had convictions quashed are eligible for £600,000 payouts.