She served as chief executive from 2012 to 2019, and has faced questions about why hundreds of subpostmasters were wrongly convicted of fraud and false accounting under her watch.

Scrutiny grew after she was depicted in the ITV docudrama Mr Bates vs The Post Office - and she gave back her CBE after the programme sparked public anger.

When she returned her honour, Ms Vennells had said: "I have so far maintained my silence as I considered it inappropriate to comment publicly while the inquiry remains ongoing and before I have provided my oral evidence.

"I now intend to continue to focus on assisting the inquiry and will not make any further public comment until it has concluded."

Alan Bates will also be giving evidence to the inquiry when it resumes in April - as well as Lord Arbuthnot, who campaigned on behalf of subpostmasters during his time as an MP.

Former business secretary Sir Vince Cable and current Lib Dem leader Sir Ed Davey, who previously served as postal affairs minister, will also testify.