Most British papers are saying it was due to cladding backed by polyurethene, a highly flammable substance that pushed the flames higher very quickly.  Also--lack of sprinkler systems, which the Tories refused to have installed because 'it would hinder developers from 'building new housing.'  In other words, not the proverbial Islamic threat, but neoliberal policies and deregulation.  This was shown by the fact that a safety report was tabled in parliament after a similar fire in a housing estate in southeast London that killed 6 people in 2009.  The report recommended sprinklers and non-flammable cladding, it was ignored by the Tories.