Four fire engines and around 25 firefighters were called to a fire at a derelict building on Harrow Weald in Harrow.
A derelict two-storey building was destroyed by the fire. There were no reports of any injuries.
The Brigade was called at 0508 and the fire was under control by 0711. Fire crews from Stanmore and Harrow fire stations attended the scene.
The cause of the fire is under investigation.