Four fire engines and around 25 firefighters were called to a fire at a restaurant with dwellings above on Belmont Hill in Lewisham.
The ground floor, first floor and staircase from the ground to first floor of the three storey building were completely destroyed by fire.
Two people left the building before the Brigade arrived with another two people evacuating from neighbouring properties. Thankfully no injuries are reported.
It's believed there were no working smoke alarms in the property.
A London Fire Brigade spokesperson said: "This incident also shows just how important it is to have working smoke alarms fitted on every level of your home.
“Smoke alarms give the earliest possible warning when a fire starts and we would urge everyone to make sure they have one fitted in every room where a fire can start except kitchens or bathrooms where heat alarms are more appropriate.”
The Brigade was called at 0100 and the incident was under control by 0318. Fire crews from Lewisham, Lee Green, Deptford and New Cross fire stations were at the scene.
The cause of the fire is under investigation.