Six fire engines and 35 firefighters and officers were called to a fire at a block of flats in Flood Street in Chelsea.
Part of a first floor flat was damaged by fire.
Nobody was home at the time of the fire and the alarm was raised after a neighbour heard a smoke alarm sounding.
The Brigade was called at 0839 and the fire was under control at 0958. Fire crews from Chelsea, Battersea, Fulham, Lambeth and Kensington fire stations attended the scene.
The cause of the fire is believed to have been reflected sunlight from a mirror igniting curtains.