Reports suggest that two types of cladding were added.  One was to make the building more energy efficient.  The other was to make the building look  nice, so that rich neighbors were not offended by the sight of council housing from their property.   Reports suggest that their was a gap of possibly 30 cms between the two, creating a potential chimney for fire to spread.  It is also stated that the outer, sham, cladding was flammable and had been banned, variously in the US, Europe and possibly in UK, over a certain height on buildings.  Some 120 buildings around the country are now said to be covered in this cladding.
      The comments above have been qualified because at this stage of the tragedy nothing can be stated with certainty;  other than the sorrowful figures of people dead and missing presumed dead.