Grenfell Tower victims had more than half an hour to escape the high-rise block before the stairs filled with toxic smoke, but were told to stay put by the fire service, the official inquiry was told on Monday.

The failure to evacuate the building immediately by the London Fire Brigade (LFB) may have “made all the difference between life and death”.

An official report revealed that the controversial “stay put” strategy had “substantially failed” by 1.26am when flames could be seen to have reached the top of the 23-storey tower block.

It said the building remained “tenable for escape” while the stairwells stayed smoke-free, which was until at least 1.30am. But it would take the fire service until 2.47am – 41 minutes after it had declared the disaster a “major incident” – to abandon the advice and instead encourage residents to evacuate.

The inferno on June 14 last year claimed the lives of 72 people in the single-greatest loss of life to a fire in a residential building in Britain since the war. No one who lived below the 11th floor died.