The company that sold the combustible panels that spread the Grenfell Tower fire was warned a decade before the disaster that such material burns like fuel oil, releases lethal toxic smoke and could become involved in a fire killing up to 70 people, the public inquiry into the disaster has heard. In an uncanny foreshadowing of the June 2017 disaster that claimed 72 lives, an executive from Arconic attended a seminar in Norway in 2007 where a cladding expert raised the question of a manufacturer’s responsibility if a “building made out of polyethylene (PE) core” cladding were to catch fire, killing “60 to 70 persons”. Gerard Sontag, the Arconic executive who attended the seminar, reported back to the company that he was so concerned by the expert’s warning that Arconic should consider only selling the panels with a fire retardant (FR) core, but that didn’t happen. The firm went on to sell its PE product for use on Grenfell and it became the main cause of fire spread, engulfing the 24-storey block in less than 30 minutes and fuelling the worst loss of life in a single incident in London since the second world war. The revelation came as the inquiry “empty chaired” three witnesses from Arconic’s French division, including its technical chief, Claude Wehrle, who have refused to face questioning. Counsel to the inquiry, Richard Millett QC, instead raised questions he would have asked and disclosed internal documents that delivered fresh revelations about what the wing of the US company knew of the risks posed by its products. Millett showed that in June 2011, Arconic warned a Spanish customer not to use its PE panels because they achieved the low fire performance rating E, which the customer remarked was “close to spontaneous combustion”. But in 2014, Arconic sold the same panels to the Grenfell project on the basis of a UK fire performance certificate that suggested the materials were rated B. Millett showed that, in the months after April 2015, when Arconic processed a purchase order selling the PE panels for Grenfell, executives shared technical reports about 10 high-rise fires in different parts of the world using similar cladding panels, warning of the risks. Wehrle was sent a report about a 2014 cladding fire in the Lacrosse building in Melbourne in early May that warned about the “speed and intensity of fire spread”, rising from the eighth to the 21st storey in no more than 15 minutes and penetrating rooms on each floor, a similar pattern to the fire’s progress at Grenfell. The same report showed eight other high-rise fires with very similar cladding around the world. In October 2015, colleagues sent Wehrle pictures of a cladding fire at a medical centre in Saudi Arabia that had used fire retardant panels, where the fire was limited to the lower storeys. Wehrle remarked: “In PE, the fire would have spread over the entire height of the tower, while in this case only the area near the fire is affected. Long live FR :-)” In January 2016, after a cladding fire at the Address hotel in Dubai involving PE panels, Wehrle emailed colleagues saying: “I hope that PE will be gradually excluded from facade cladding.” Millett asked why Wherle had “hoped” PE would be excluded when Arconic was continuing to manufacture it and sell it. Later that month there was another fire in the Wolleck tower in France, only 10 metres from a building clad in Reynobond PE. Wehrle told colleagues they were “very lucky” the wind had not changed direction and spread the fire. “We really need to stop proposing PE in architecture! We are in the ‘know’, and I think it is up to us to be proactive … AT LAST.” Grenfell Tower caught fire 17 months later. “What happened to Mr Wehrle’s warning to senior management?” said Millett. “Did they do anything about this and if so what?” The inquiry continues.