Fire crews were called to a blaze started by a candle lit to commemorate the beginning of the First World War.
It is believed the candle was lit as part of the Lights Out event which encouraged people to turn off their lights for an hour until 11pm on Monday - the time war was declared in 1914.
Firefighters were called to the property in Whitehill Road, Cambridge, at 12.18am on Tuesday.
A spokesman for Cambridgeshire Fire and Rescue Service said: " The occupant of the first-floor flat was out of the building before crews arrived.
"Firefighters had to force entry to a ground-floor flat and led a resident to safety."
A fire investigation found t he most likely cause of the fire was an accident, due to the lit candle being left on a windowsill and spreading to curtains, which then developed and spread through the property.