Fujitsu’s European boss who said the technology giant has a “moral obligation” to contribute to compensation for subpostmasters is set to give evidence to the Post Office Horizon IT inquiry.

Paul Patterson, the director of Fujitsu Services Ltd, faces his second grilling of the week after appearing at the Business and Trade Committee on Tuesday.

Mr Patterson previously apologised to subpostmasters who had been wrongly convicted as a result of problems within the Horizon software – conceding there were “bugs and errors in the system”.

On Friday, he will answer questions in phase four of the public inquiry which is looking at the action taken against subpostmasters – including civil and criminal proceedings and failures in investigations.

The statutory inquiry, which began in 2021, was established to ensure there was a “public summary of the failings which occurred with the Horizon IT system at the Post Office” and which subsequently led to the wrongful convictions of subpostmasters.

The probe is chaired by retired judge Sir Wyn Williams, who has previously looked at the human impact of the scandal, the Horizon system rollout and the operation of the system.

Since Tuesday, a number of Fujitsu witnesses – including security team managers and software developers – have been quizzed on their roles when dealing with problems reported by subpostmasters, and subsequent prosecutions.

One Fujitsu manager, Peter Sewell, faced a number of questions about a 2006 email in which he labelled subpostmaster Lee Castleton a “nasty chap” who will be “all out to rubbish” the company’s name ahead of legal proceedings which led to his bankruptcy.

Another witness, Rajbinder Sangha, a former member of Fujitsu’s fraud and litigation support office, told the probe this week that data from the scandal-hit Horizon system is still being used in court proceedings.

Software developer Gerald Barnes said problems have been identified with audit data provided to the Post Office by Fujitsu as late as August last year.

Mr Barnes said 13 transactions were missing in the “unreliable” data provided as part of an ongoing Court of Appeal case relating to a former subpostmaster of the Apex Corner branch in London.

Staff from Fujitsu software support centre, including team leader John Simpkins, feared being “hauled over the coals” after realising the Post Office was using “manipulated” audit data to criminally investigate subpostmasters.