A picture of an enormous corporate scandal has emerged at the Grenfell Tower inquiry to little fanfare over the last three weeks. The mammoth inquiry has been slowly going through the evidence surrounding the build-up to the fire, which killed 72 people in June 2017. Until November, it had been examining the fitting of the deadly cladding system to the walls of the building. What the inquiry revealed was dispiriting but predictable: pennies were pinched, no one in an enormous chain of construction professionals took responsibility for key safety decisions, and the external oversight of their actions was almost non-existent. In recent weeks though, the tone of the inquiry changed, and the revelations have become considerably more startling.

Officially, the inquiry has been examining the testing, marketing and sale of the combustible plastic materials which were attached to the walls of the tower...

This chiefly means three products: the actual cladding panels (thin aluminium sheets bonded to a core of polyethylene, a plastic with similar properties to solid petrol) and two forms of combustible foam insulation which were fitted behind it.

These materials were made and sold by companies which are huge global players. The cladding came from the French arm of Arconic, a Pennsylvania-based giant with £5.4 billion in global turnover... The insulation was sold by Celotex, a medium-sized UK company..., and Kingspan, an Irish giant with more than £3 billion in annual turnover and almost 14,000 employees.

What has emerged is evidence which suggests each of these firms were aware their products posed serious fire risks, but this was concealed from both regulators and the market so they could be sold for use on high rises...

The three firms involved in the Grenfell cladding have all denied responsibility for the disaster: Celotex emphasises that it had no design responsibility, and that compliance was a matter for the professionals who refurbished the tower. It said it repeated the allegedly distorted test without discrepancy in 2018. Kingspan says it did not pursue the Grenfell Tower job, knew nothing of the specific design and has now passed numerous tests with K15 insulation which supported its historic marketing claims, as well as its occasional failures. Arconic says that its cladding should not have been used on the tower in the way it was and has pointed to other critical issues with the installation, such as the use of insulation and inadequate fire barriers.