The Royal Standard rescued by Sir Ernest Shackleton from his doomed ship, the Endurance, has been sold at auction for £116,000.
The flag, presented to the explorer in 1914 by the dowager Queen Alexandra before he set off on his historic voyage to the Antarctic, went to an anonymous buyer.
The UK's National Maritime Museum had launched an urgent appeal to secure the standard for its archives.
"We didn't make it," a spokeswoman for museum said.
The painted silk standard was one of only two things that Shackleton saved from his ship before it was crushed in the winter ice.
The explorer then carried the flag inside his coat as he and his men set out on their heroic journey to Elephant Island.
Shackleton, who has been celebrated in several recent books and films, eventually found help in South Georgia after making a 1,300-kilometre (800-mile) journey across treacherous seas in a small open boat.
"Shackleton took the standard with him all the way through the Endurance expedition, an extraordinary epic of survival which has had huge worldwide acclaim in the past few years," Jonathan Shackleton, the family historian, told BBC News Online last week.
The museum had attempted to buy the flag the last time it came up for auction in 1999.
Christie's pre-sale estimate for the flag was £100,000 to £150,000.
~RS~a~RS~International~RS~q~RS~~RS~z~RS~44~RS~)