Six fire engines and around 40 firefighters were called to a fire at a flat in Bittern Street in Southwark.
A five-roomed flat on the third floor of a four-storey block was destroyed by the fire. Part of the roof was also damaged. There were no reports of any injuries.
The Brigade’s 999 Control Operators took 34 calls about the fire.
The Brigade was called at 1510 and the fire was under control at 1720. Fire crews from Dowgate, Dockhead, Lambeth, Old Kent Road and Whitechapel fire stations attended the scene.
The Brigade's fire investigation team believe the cause of the fire was a carelessly discarded cigarette.