The question of what Paula Vennells knew and when she knew it is a central area of interest.

The first alarm was raised by Alan Bates, played by Toby Jones in the ITV Drama Mr Bates vs The Post Office, in 2003. However an apology was not issued by the Post Office until 2019.

One of the likely questions Ms Vennells will be asked will be around the remote access IT staff could get to Post Office branches’ accounts.

People at Fujitsu, the company who made the Horizon IT system, and the Post Office IT helpdesk could edit sub-postmasters’ accounts.

This remote access is relevant because it would have called into question the claim that sub-postmasters were to blame for the shortfalls in their accounts, for which they were prosecuted.

Sky News obtained a secret recording from 2013 that suggests Ms Vennells had been told about the remote access.

In 2010, before she had even taken up her post, Post Office prosecutors were alerted to bugs with the Horizon system.

The question is, if she did know about the issues with Horizon, why did she not scrap the system and raise the alarm to prevent further prosecutions of innocent sub-postmasters?