Four fire engines and around 25 firefighters tackled a fire at a mid terrace office building on Grosvenor Hill in Mayfair.
A small part of a plant room in the basement was damaged by the fire. Around ten people left the building before the Brigade arrived. There are no reports of any injuries.
Control Officers took the first of two calls at 0743 and mobilised crews from Soho, Euston and Paddington fire stations to the scene. The fire was extinguished by 0917.
The fire is believed to have been accidental and was caused by an electrical fault.