Six fire engines and 35 firefighters and officers were called to a fire at an office block in St John Street, Clerkenwell.
Part of the basement and part of the ground floor of the building was damaged by fire.
The Brigade was called at 0321 and the fire was under control at 0558. Fire crews from Soho, Shoreditch, Islington, Euston and Dowgate fire stations attended the scene.
The cause of the fire is under investigation.