Former staff of insulation company Celotex continued giving evidence to the Grenfell Tower Inquiry this week, providing a detailed picture of the extreme lengths to which the firm went to get a combustible product portrayed as safe for use on high-rise buildings.

On Monday ex-product manager Jonathan Roper said the firm had exploited “ignorance” about fire-testing regimes within the construction industry to sell its flammable RS5000 polyisocyanurate (PIR) product as suitable for use on structures above 18m in height.