Ten fire engines and around 70 firefighters tackled a fire at an end-of-terrace house converted into flats on Lyncroft Gardens in West Hampstead.
Half of the roof of the building and part of a third-floor flat were damaged by fire. Firefighters evacuated around 25 people to safety. There were no reports of any injuries.
Station Commander Ken Spratt, who was at the scene, said: "One of the Brigade's 64-metre turntable ladders was used at the scene as a water tower to tackle the fire from height. Drones were also used to survey the incident from above, providing incident commanders with an aerial view to support with developing tactics.
"West Hampstead Fire Station has been set up as a rest centre for residents affected by the fire."
The first call was made to the Brigade's Control Officers at 0309 and the fire was under control by 0523. Fire crews from West Hampstead, Paddington, North Kensington, Hendon and surrounding fire stations attended the scene.
The fire is believed to have been accidental and caused by hot works that had been taking place.