Twelve fire engines and around 80 firefighters tackled a flat fire on Cadogan Square in Belgravia.
The mansard roof of a mid-terraced block of flats was destroyed by fire. The fourth-floor of a split-level maisonette was also destroyed by the blaze and part of the third floor was damaged. Around 15 people left the building before the Brigade arrived. There were no reports of any injuries.
The Brigade's 999 Control Officers took 22 calls to the blaze.
Station Commander Matt Cole, who was at the scene, said: "The fire was in the roof space of the building and crews worked incredibly hard to bring it under control.
"One of the Brigade's 32-metre turntable ladders was used to get water on to the building externally from height.
"Cadogan Square was closed and there were severe delays, so we asked people to avoid the area where possible.
"Crews remained on scene throughout the evening."
The Brigade was called at 1346 and the fire was under control by 1632. Fire crews from Soho, Lambeth, Chelsea and surrounding fire stations attended the scene.
This fire is believed to have been accidental, caused by hot works being carried out on a flat roof.