Four fire engines and around 25 firefighters tackled a fire at a pub with flats above on Mansell Street in Tower Hill.
Most of an electrical intake room on the ground floor of the building was damaged by fire. Around 20 people left the pub before the Brigade arrived. Firefighters wearing breathing apparatus led a woman to safety from the first floor of the building due to smoke logging in the corridor. There were no reports of any injuries.
A 20-metre cordon was put in place as a precaution whilst crews worked to make the scene safe.
The Brigade was called at 1937 and the fire was under control by 2157. Fire crews from Whitechapel, Shadwell, Dowgate and Shoreditch fire stations attended the scene.
The cause of the fire is under investigation.