Four fire engines and around 25 firefighters were called to a fire at a block of flats on Dove Park in Pinner.
Part of a four-roomed flat on the first floor of an eight-storey block was damaged by the fire. Two adults and two children left the affected flat before the Brigade arrived and a woman from a neighbouring flat was assisted to the ground floor by firefighters and assessed by London Ambulance Service crews.
The Brigade was called at 2025 and the fire was under control by 2148. Fire crews from Harrow, Stanmore and Northolt fire stations were at the scene.
The cause of the fire is believed to be accidental.