Seventy-two firefighters were called to a fire in Dartmouth Park Hill, Archway, over the weekend.
Ten crews attended the blaze in a terraced block of flats at about 8pm on Saturday.
Two neighbouring properties sustained the same damage. Both roofs were destroyed and about 80 per cent of the second floors were damaged.
One woman left the building before the brigade arrived and was treated at the scene by London Ambulance Service. About 20 people were evacuated from adjoining flats as a precaution.
The fire was under control just after midnight. The cause is under investigation.
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