The director of one of the manufacturers of Grenfell Tower’s combustible insulation has stepped down amid controversy. Peter Wilson, the managing director of Kingspan’s insulation boards division is due to stand down after evidence emerged which showed his company used out of date fire tests to market material that it knew could burn ‘like a raging inferno’.

Wilson had overseen Kingspan’s insulation division since 2001 and had been in charge for the Kooltherm K15’s (K15) launch. K15 is a plastic foam insulation that was used in the Grenfell tower. Though K15 passed safety tests in 2005, Kingspan changed its chemical composition – making it more flammable. Despite the clear increase of flammability, Kingspan continued to use the previous test pass and claimed the K15 was safe for tall buildings.

Lawyers that have acted for the bereaved and survivors, including Adrian Williamson QC and Sam Stein QC have said that firms and regulators operated in a ‘toxic and incestuous culture’.

The inquiry also heard that after the tragic fire in June 2017, Kingspan rigged tests and hired lobbyists to try to persuade MPs that rival non-combustible products might be no less dangerous than their combustible material.

The inquiry also revealed text messages from Kingspan staff that joked about the K15 safety tests, labelling them ‘all lies’. One of the staff members, sent this text to a colleague in 2016: ‘Yeahhhh. Tested K15 as a whole – got class 1 [a worse performance]. Whey. Lol.’ The K15 made up around 5% of the insulation used on the Grenfell Tower.

Gene Murtagh, Kingspan chief executive, stated that further action would be required to ensure the historical shortcomings were not repeated.

Though shortly before evidence regarding Kingspan was revealed at the public inquiry, that led to a price fall, Wilson sold shares worth £1.6m and Murtagh sold shares worth £3.1m—sparking anger among both bereaved and survivors.

Kingspan executives will continue giving evidence when the inquiry is due to resume on 11 January.