A Post Office investigator who has been described as having a “heavy footprint” in the Horizon IT scandal is due to give evidence for the inquiry’s first hearing of the year.

The statutory inquiry, which began in 2021 and is chaired by retired judge Sir Wyn Williams, has previously looked at the human impact of the scandal, the Horizon system roll-out and the operating of the system, and is now probing the action taken against subpostmasters.

The probe was established to ensure there is a “public summary of the failings which occurred with the Horizon IT system at the Post Office” and subsequently led to the wrongful convictions of subpostmasters.

Stephen Bradshaw is scheduled to give evidence on Thursday after being involved in the criminal investigation of nine subpostmasters, including Lisa Brennan, a former counter clerk at a post office in Huyton, near Liverpool, who was falsely accused of stealing £3,000 in 2003.

Mr Bradshaw has also been accused by fellow Merseyside subpostmistress Rita Threlfall of asking her for the colour of her eyes and what jewellery she wore before saying: “Good, so we’ve got a description of you for when they come” during her interview under caution in August 2010.

Lead counsel to the inquiry Jason Beer KC previously described Mr Bradshaw as having a “heavy footprint” in the scandal.

His evidence will form part of phase four of the Post Office Horizon IT Inquiry which began in July last year and is looking at the action that was taken against subpostmasters including audits, investigations and criminal proceedings.

Mr Bradshaw was due to answer questions in November, but disclosure failings from the Post Office meant the hearing was delayed until Thursday.

Earlier in phase four, a former Post Office lawyer apologised for prosecuting Ms Brennan who was left homeless with her young daughter after being wrongly convicted of theft.

Theresa Williamson said she was “angry” that material concerning the faulty computer system was not disclosed to her before Ms Brennan’s prosecution, saying: “We should have been told these things.”

The actions of other lawyers and investigators have also come under scrutiny from Mr Beer and his team over the past few months.

In September last year, former legal case manager Mandy Talbot told the probe she had “nothing to hide” despite appearing to suggest dealing with a subpostmistress’s claim of system defectiveness by saying: “How much to go away and keep your mouth shut?”

In the same month, former Post Office auditor Helen Rose was grilled over giving “inaccurate” information to the High Court which led to the bankruptcy of East Yorkshire subpostmaster Lee Castleton.

In July, the head of legal services at the Post Office, Ben Foat, also apologised at the inquiry after a document surfaced which used the racist term “negroid types” to describe wrongly convicted subpostmasters.

The inquiry has also been littered with delays because of disclosure failings from the Post Office.

In November, Mr Beer said around 363,000 emails had been found on a legacy mailing system, and said the previous disclosure failings had led some to use the phrase “cover up”.

Phase four of the inquiry is due to last until the beginning of next month.