Twelve fire engines and around 80 firefighters were called to a fire at a ground floor shop with flats above on Back Hill in Clerkenwell.
The ground floor was destroyed by the fire and most of the first floor was damaged. Four people left the building before the Brigade arrived. There were no reports of any injuries.
Station Manager Paul Eastland, who was at the scene, said: "There was a lot of visible smoke coming from the fire so residents and local businesses were advised to keep their windows shut."
The Brigade’s 999 Control centre received 12 calls alerting them to the fire.
The Brigade was called at 0611 and the fire was under control by 0954. Fire crews from Soho, Shoreditch, Islington, Dowgate, Whitechapel, Lambeth, Euston and Paddington fire stations were at the scene.
The fire started in the rear store cupboard and the cause of the fire is believed to be electrical.