Four fire engines and 21 firefighters and officers attended a fire at a disused sports centre on Headstone Drive in Harrow.
A small part of the derelict building was damaged by fire
The Brigade was called at 0750 and the fire was under control by 0825. Fire crews from Harrow, Stanmore and Wembley fire stations were at the scene. The cause of the fire is not known at this stage.