The first floor of a semi-detached house was damaged by the fire. Four people left the property before the Brigade arrived. There were no reports of any injuries.
Station Officer Tony Aston-O’Donovan, who was at the scene, said: “Crews arrived to find a fully developed fire on the first floor of the building.
“They quickly gained access and firefighters worked hard to bring the fire under control.
“There were smoke alarms in the property but they weren’t working and the occupants awoke to find smoke inside.
“Fortunately, they were able to get out immediately and call 999 but they were incredibly lucky.
“This is a reminder of the importance of having working smoke alarms in your home. They give the earliest possible warning to fire, providing time to escape.
“You should have smoke alarms in every room where a fire could start, plus a heat alarm in the kitchen.”
The Brigade was called at 3.08a and the fire was under control by 4.39am. Four fire engines and around 25 firefighters from Wembley and Hendon fire stations were at the scene.
The cause of the fire is under investigation.