Who will be giving evidence at the Post Office Horizon IT inquiry?

Alan Bates, the former subpostmaster made famous by the ITV drama, Mr Bates vs the Post Office, was characteristically modest about his role as he gave evidence on Tuesday to the public inquiry into the failings of the Horizon IT system at the Post Office.

He told of finding himself leading a group of 500 subpostmasters, “stray lambs” who realised that they all felt a similar sense of injustice at the high-handed way they were treated by the Post Office. He gave up work in 2003 to pursue justice, but “I didn’t set out to spend 20 years doing this,” he told the inquiry.

The inquiry also heard how Sir Ed Davey, the leader of the Liberal Democrats and then the minister for the Post Office, refused to meet Mr Bates but was eventually persuaded to do so by his officials, for “presentational reasons”.

In the years since, the full scale of the scandal has emerged.

The inquiry is led by Sir Wyn Williams, a retired High Court judge, and was set up in 2020 “to gather a clear account of the implementation and failings of the Horizon IT system at the Post Office over its lifetime”. It was originally promised by Boris Johnson as prime minister, but was created as a non-statutory inquiry, with limited powers, and was boycotted by the Justice For Subpostmasters Alliance, which called it a whitewash.

In May 2021 the government announced that it would be upgraded to a statutory inquiry, and would thus have the power to compel witnesses to give evidence. The original intention was that it would deliver its findings in autumn 2022, but one of the drawbacks of a statutory inquiry is that it tends to take longer.

No date has been set for the final report, but closing statements will be in late July this year. The Post Office has been accused of trying to delay the inquiry, including by late disclosure of documents. The session on Tuesday began with the inquiry’s lawyer revealing that another 73,000 documents had been submitted over Easter. However, the inquiry chair has insisted that he will not allow such tactics to delay his report any further, and that he will recall witnesses if new information comes to light after their evidence.

Paula Vennells, the chief executive of the Post Office from 2010 to 2019, is probably the most important witness. She has not spoken in public about the scandal since her time in the job. She has already handed back her CBE. She is expected to give evidence over three days from 22 May, and is likely to be asked about recent evidence that she knew earlier than previously admitted that the Horizon system was faulty.

Adam Crozier, who was chief executive of Royal Mail from 2003 to 2010, when Royal Mail owned the Post Office.

Lord Arbuthnot, the former Conservative MP who campaigned for the subpostmasters for 14 years in what many regard as a shining example of what a backbencher can achieve.

David Mills, Alan Cook, David Miller and David Smith, managing directors of the Post Office during the period from 2003 to 2010, when most of the wrongful prosecutions occurred.

Mark Davies, Post Office spin doctor. He clashed with the BBC when Panorama made a programme about the scandal in 2015.

The inquiry will also hear from a succession of ministers who were responsible for the Post Office: Sir Ed Davey, Pat McFadden, Greg Clark and Vince Cable.

Finally, it will hear from Duncan Tait, the former chief executive of Fujitsu, the IT company that supplied the Horizon system, who is said to have told Ms Vennells that it was as strong as “Fort Knox”; Gareth Jenkins, a Horizon engineer at Fujitsu who was involved in several prosecutions of subpostmasters; and from Ron Warmington and Ian Henderson, forensic accountants, who were sacked by the Post Office and who were also portrayed in the ITV drama.