Four fire engines and around 25 firefighters were called to a fire in Grays Inn Road, Holborn.
The fire was contained to an external stairway that led to a basement flat. There were no reports of any injuries.
The Brigade was called at 1724 and the fire was under control by 1809. Crews from Euston, Soho, and Shoreditch Fire Stations attended the incident.
The cause of the fire is believed to have been the failure of an electric supply cable in the street.