Four fire engines and around 25 firefighters tackled a fire at a residential block on Stratton Street in Mayfair.
Part of an electrical intake room in the basement was damaged by fire. There were no reports of any injuries.
The Brigade was called at 1632 and the fire was under control by 1712. Fire crews from Soho, Euston and Lambeth fire stations attended the scene.
The fire is believed to have been accidental and caused by a fault within the electrical distribution board.