Defying the 1,000-hour life expectancy of a light-bulb, the one shining in a Briton's porch is believed to have been glowing for last 100 years.
The 230-volt, 55-watt DC Osram bulb was reportedly made in July 1912, just months after the Titanic sank.
"At this rate, it'll burn for ever!," said 74-year-old Owner Roger Dyball about the bulb which still lights his porch in Lowestoft, Suffolk.
The bulb had already been in place at Dyball's home near Lowestoft, in Suffolk, when he and his wife Patricia moved in 45 years ago.
"We found it with its original fittings when we moved here in 1967 and it has never gone out," said Dyball.
Dyball was so intrigued by the bulb manufactured in Wembley, North London that he wrote a letter to company Osram-GEC's London head office with its serial number and other details.
Osram worked out its date of manufacture and gave him a special certificate.
In a reply, dating back to January 30, 1968, the company said the bulb was manufactured sometime in July 1912.
Britain's oldest working bulb was found at Margate, Kent, in 2008. Experts estimated it was made in 1895 - 15 years after US genius Thomas Edison invented the light bulb.
Modern bulbs last an average 1,000 hours before conking out.