Executives who sold combustible insulation for use on Grenfell Tower perpetrated a “fraud on the market” by rigging a fire test and making “misleading” claims about it, a public inquiry has heard. Celotex, a subsidiary of the French construction materials company Saint-Gobain, behaved in a “completely unethical” way, admitted Jonathan Roper, a former assistant product manager. Roper worked on two fire tests of the foam panels and subsequent sales plans as the company tried to grab a slice of a £10m-a-year insulation foam market. In the Grenfell fire on 14 June 2017, the foam, known as RS5000, fuelled the flames and released toxic gases and smoke. The foam was withdrawn from the market nine days later. In evidence to Grenfell inquiry’s examination of the manufacture, testing and sale of the largely plastic materials, Roper said the firm had been “dishonest” by “over-engineering” a cladding fire safety test to achieve a pass. A first test in February 2014 failed in 26 minutes, with flames engulfing the rig. But after changing some of the materials used around the insulation, including adding concealed fire-retardant panels, a second test three months later passed and was used to market the foam boards as safe for high-rise buildings. Roper was asked to produce slides for the sales team that would not include mention of the earlier failed test or the fact that the magnesium oxide board had been added in the second test. The slide was “downright misleading” and “intended to mislead”, he agreed under cross-examination by Richard Millett QC, counsel to the inquiry. “Did you realise at the time that … this would be a fraud on the market?” asked Millett. “Yes, I did,” replied Roper. “I felt incredibly uncomfortable with it. I recall going home that evening, I was living with my parents at the time, and mentioning it to them. I felt incredibly uncomfortable with what I was being asked to do.” Asked if he could have gone to the senior management with his concerns, he replied that they were all in the meeting about the marketing strategy. “I went along with a lot of actions at Celotex that, looking back on reflection, were completely unethical and that I probably didn’t potentially consider the impact of at the time,” he said. “I was 22 or 23, first job, I thought this was standard practice, albeit it did sit very uncomfortably with me.” Celotex has told the inquiry that “the combustible nature of [its insulation] was, or should have been, known to construction professionals”. It has accepted that the circumstances around the testing, certification and marketing of the materials involved “unacceptable conduct” by some employees and said it has “taken concerted steps to ensure that no such issues reoccur”. The group has also said it promoted RS5000’s use on buildings that are taller than 18 metres only in a “rainscreen cladding system with the specific components”, used when it passed the fire safety test. The inquiry continues.