A retirement home in Twickenham was set alight after someone threw away a cigerette.
The common room at Somerville House in Rodney Road, which contains around 30 apartments, was damaged by fire on Thursday (August 3) night.
Four fire engines and around 20 firefighters and officers were called to the blaze
London Fire Brigade (LFB) said a small part of the ground floor common room in the two-storey building was damaged by fire.
LFB said the fire is "believed to have been caused by discarded smoking materials".
The alarm was raised when a smoke alarm sounded alerting a monitoring centre who then called for emergency help at around 10.30pm.
Smokers are now being reminded by LFB to take extra care when discarding their cigarettes at home.
An LFB spokesman said: "If you are a smoker, it is vital that you take extra care and ensure your cigarette is completely out when you’ve finished smoking it.
"If you don’t, you risk causing a fire which could not only destroy your home, but also cost you your life."
No injuries were reported in the fire, which took the brigade just over one hour to control.
Fire crews from Twickenham and Heston fire stations attended.
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