Six fire engines and around 40 firefighters were called to a fire at a restaurant with flats above on Long Elmes in Harrow.
The restaurant was destroyed by fire. Five people left the building before the arrival of the Brigade.
The Brigade's 999 Control Officers received 20 calls to the fire.
The Brigade was called at 0242 and the fire was under control at 0516. Fire crews from Harrow, Stanmore, Northolt, Wembley and Finchley fire stations attended the scene.
The cause of the fire is under investigation by the Brigade and the Metropolitan Police Service.