Six fire engines and around 40 firefighters were called to a fire at a community centre on Legion Way in North Finchley.
A marquee was destroyed by fire and most of a single-storey community centre was damaged by the blaze. Firefighters wearing breathing apparatus led a man to safety from a purpose built cabin at the front of the building. There were no reports of any injuries.
The fire originated in a marquee at the rear and spread into an adjoining building.
The Brigade was called at 0240 and the fire was under control by 0504. Fire crews from Finchley, Hendon, Hornsey, Kentish Town, Northolt and Park Royal fire stations attended the scene.
The fire is believed to have been accidental.