Eight fire engines and around 60 firefighters were called to a fire at a derelict pavilion on Preston Road in Harrow.
Firefighters tackled a fire at a derelict pavilion on grassland, which was completely destroyed. There were no injuries reported.
The Brigade's Control Officers received 23 calls about the fire.
The Brigade was called at 1748 and the fire was under control by 2001. Fire crews from Wembley, Stanmore, Northolt, Mill Hill and other surrounding fire stations attended the scene.
The cause of the fire is under investigation by the Brigade and the Metropolitan Police Service.