From the fourth floor, the fire spread rapidly upwards and across the eastern side of the building. From there, it spread across the north face of the tower. Mobile phone videos show the blaze reaching the top floor on the east side of Grenfell Tower by about 01:26, less than 30 minutes after firefighters had arrived. In a report to the Grenfell Public Inquiry, fire safety engineer Dr Barbara Lane identified the fire spreading vertically up the tower columns, and “laterally along the cladding above and below the window lines (and) the panels between windows.” The fire had spread to the north side of the tower by 01:42, Dr Lane recorded. At 01:52, the fire also began travelling across the eastern side towards the south in the other direction.
At 02:06, London Fire Brigade declared the fire a “major incident”. At this point, some 40 fire engines were either at or en route to the scene. Grenfell Tower had a ‘stay put’ fire policy – essentially, the building design would contain a fire in a single flat for as long as it took fire crews to bring it under control. So on the night, many residents were told to remain in their flats by the emergency services, only to become trapped as the fire blazed out of control and thick poisonous smoke spread up the single narrow stairwell. Dr Lane said that the stay put policy had “substantially failed” by 01:26 – less than 30 minutes after the first firefighters were at the scene. Some people ignored the stay put advice and made it down the stairs to safety.