The former product manager at the firm which manufactured the flammable insulation boards used on Grenfell Tower’s flawed refurbishment has called the actions of his former employer “completely unethical”, the inquiry has heard.

Jonathan Roper, who worked at Celotex between May 2012 and September 2014, told Monday’s hearing how the insulation manufacturer deliberately exploited “ignorance” within the construction industry about fire testing regimes to sell its combustible RS5000 product for use on high rise buildings.