A senior material testing technician has denied being aware that a fire test of a Celotex insulation product later installed on Grenfell Tower included extra components to ensure a pass, the inquiry into the 2017 fire has heard.

Phil Clark, former cladding test chief supervisor at testing body the Building Research Establishment (BRE), said that manufacturers of combustible materials were able to “sneak” extra components onto test rigs without inspectors knowing.