Four fire engines and around 25 firefighters attended a house fire on St John's Hill in Wandsworth.
Part of the ground floor of a terraced house was damaged by fire. There were no reports of any injuries.
The Brigade was called at 1052 and Control Officers mobilised crews from Wandsworth, Clapham, Tooting and Fulham fire stations to the scene. The fire was extinguished by 1207.
The fire is being treated as accidental and believed to have been caused by refracted sunlight.