Two fire engines and around 10 firefighters were called to a fire in the roadway on Great Peter Street in Westminster.
A diesel powered generator was destroyed by the fire. There were no reports of any injuries.
The Brigade's 999 Control Officers took 27 calls about the fire.
The Brigade was called at 1102 and the fire was under control by 1141. Two fire engines from Lambeth Fire Station attended the scene.
The cause of the fire is under investigation.