London, UK – The aluminium composite material (ACM) rain screen was the 'principle reason' why flames rose up the side of the Grenfell Tower. The panels had a flammable polyethylene core, which acted as a source of fuel.
This is one of the key findings in the leaked first stage report from the Grenfell inquiry, and published by the UK's Daily Telegraph newspaper. In the months leading up to the fire, the tower's external walls were refurbished, and an ACM crown was added to the building. That work did not meet building regulations.