When Ed Daffarn opens his door in the early hours of the morning of the 14th of June 2017, he is confronted by a wall of thick acrid smoke.

As the combustible cladding and insulation burned, smoke gathered rapidly in the hallways and stairwells of Grenfell. It prevented many residents from leaving their flats - and ultimately, it is the smoke which killed those who died in the tower.

The reason this smoke spread so quickly through the building is due to one small detail, which could easily be considered as inconsequential, but on the night of the fire was far from it.

Presenter: Kate Lamble Producer: Josephine Casserly Production coordinator: Janet Staples Audio engineers: James Beard and Gareth Jones Story consultant: Simon Maybin Editor: Penny Murphy