Four fire engines and around 25 firefighters were called to a fire at a house on Stanstead Road, Catford.
A passer-by saw flames and banged on the window of the property before running to nearby Forest Hill Fire Station to alert firefighters. A woman was led to safety by firefighters wearing breathing apparatus. A man left before the arrival of the Brigade. They were both uninjured.
There were no working smoke alarms in the property.
A London Fire Brigade spokesperson said: “This incident shows just how important it is to have working smoke alarms in 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.”
Part of a first floor bedroom was damaged by the blaze.
Fire crews were mobilised at 2225 and the fire was under control at 2323. Fire crews from Forest Hill, Lewisham, Greenwich, and New Cross fire stations attended the scene.