A key figure behind the software at the heart of the sub-postmaster Alan Bates, who led the campaign for justice.
Here are five things we have learned from his first day at the inquiry.
1. Jenkins denied he was ‘chief architect’ of the system
Mr Jenkins’s involvement with the Post Office IT system began in 1996 when he was asked to design features of the Horizon programme. From 2008 to 2015 he worked on Horizon Online.
After retirement, he was on a retainer to work as a consultant for Fujitsu until 2022.
Previous evidence from the inquiry suggested he was the key figure behind the Horizon system used by the Post Office.
Another Horizon manager, David McConnell, while giving evidence referred to Mr Jenkins as the “chief architect”.
Mr Jenkins rejected the suggestion he was the “chief architect” of Horizon, saying it was another engineer, Alan Ward.
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