Eight fire engines and around 60 firefighters were called to a fire at a detached house in West Heath Road, Hampstead.
Half of the roof and loft conversion were damaged by fire and part of the roof collapsed. There were no reports of any injuries.
The Brigade was called at 0025 and the fire was under control by 0248. Fire crews from Willesden, Hendon, West Hampstead and surrounding stations were at the scene.
The cause of the fire is under investigation.