The executive who sold combustible cladding for use on Grenfell Tower will face questioning for the first time this week when the public inquiry into the disaster resumes after a two-month suspension caused by the rising number of Covid cases. Deborah French, then UK sales manager at Arconic, is to be asked what she knew of the danger posed by the plastic-filled panels that the first phase of the inquiry found were the main cause of the spread of the 14 June 2017 fire, which claimed 72 lives. The hearings have seen emails from an internal discussion she had about a spate of major fires involving similar panels in the United Arab Emirates in 2013, after which she told customers her company would continue to sell both its fire-retardant and non-fire-retardant panels. In one email released to the inquiry a colleague told her the fires “will impact yourselves and the need [to make the] fire retardant core more prevalent”. French is also expected to be asked about Arconic’s knowledge of how combustible its materials were, after emails from her technical colleagues showed that warnings were circulating internally that they were not suitable for high-rise buildings. Claude Wehrle, a technical manager at the firm who is refusing to give evidence to the inquiry, knew in the years before Arconic’s panels were sold for Grenfell that they were “dangerous” and showed “bad behaviour exposed to fire”, according to emails already exposed. French asked Wehrle in 2011 if she could send a client details of the different fillings – fire retardant (FR) and polyethylene (PE). He told her: “For sure you’re NOT allowed to diffuse to the customer those documents.” He told her the “FR core is done with 30% organic part and 70% mineral part. PE is only organic. As organic is the material that is going to burn in case of a fire, FR is better”. PE was the version sold for use at Grenfell. Wehrle is one of three witnesses who worked for Arconic before the disaster who have claimed that an arcane French law called the blocking statute means they cannot give evidence. The French government has said that is not the case. Bereaved people and survivors of the Grenfell fire submitted a petition with more than 18,000 signatures to the foreign secretary, Dominic Raab, last week, urging him to apply diplomatic pressure. The inquiry confirmed it would “empty-chair” the witnesses if they did not attend. A spokesperson said: “In January, the inquiry wrote to the representatives of Gwenaëlle Derrendinger, Peter Froehlich and Claude Wehrle to confirm that, as they are still declining to attend hearings, evidence relating to them will be considered at the hearings without them having the opportunity to respond.” After initially refusing, Claude Schmidt, the president of Arconic’s French subsidiary which sold the Grenfell panels, has agreed to answer questions through an interpreter. The inquiry has already heard how Wehrle messaged Schmidt in 2009 about a fire in a building in Romania using similar panels. “Here are some pictures to show you how dangerous PE can be when it comes to architecture,” he wrote. The inquiry is to restart using Zoom video conferencing, in part because of the vulnerability to Covid of the 74-year old chairman, Sir Martin Moore-Bick. There was an outbreak among inquiry staff in December. Bereaved people and survivors have said they want a rapid return to in-person hearings. They say it would be wrong for key witnesses, particularly those from the Royal Borough of Kensington and Chelsea and the tenants management organisation, not to give evidence in front of residents. “Given the urgency of the inquiry’s work and for the reasons set out to core participants, the panel took the decision that an indefinite further delay was unacceptable, and that to proceed with remote hearings was therefore the only acceptable option available,” an inquiry spokesperson said. “Remote hearings are a temporary measure to be used only for as long as is absolutely necessary. As soon as it is safe to do so, limited attendance hearings will resume.”