Angela van den Bogerd, a former senior director at the Post Office, arrived at the Post Office Horizon IT Inquiry on Thursday morning.
She began with an apology on the first of her two days of giving evidence, telling the inquiry she was "truly, truly sorry" for the "devastation" caused to wrongly convicted sub-postmasters and their families.
Errors in the Post Office's Horizon IT system meant money appeared to be missing from many branch accounts when, in fact, it was not.
As a result, more than 700 sub-postmasters were handed criminal convictions between 1999 and 2015.
Report by Jonesia.
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