Six fire engines and 35 firefighters and officers were called to a fire at a building in Upper Wimpole Street in Marylebone.
The second floor, third floor and roof of the end of terrace building were damaged by fire.
The Brigade’s 999 control officers took more than 40 calls to reports of the fire.
People are advised to avoid the area if possible and nearby residents and businesses are urged to close all windows and doors due to smoke in the area.
The Brigade was called at 1228 and the fire was under control at 1401. Fire crews from Soho, Paddington, Kentish Town, North Kensington and West Hampstead fire stations attended the scene.
The cause of the fire is under investigatio