A postcard written by the Titanic's senior wireless operator to his sister is expected to sell for as much as £20,000.
Jack Phillips wrote the card, which carries a photograph of the Titanic on its front, to Elsie Phillips on April 6, 1912. The ill-fated liner was docked at Southampton when he penned it.
The Titanic left Southampton on 10 April for its maiden voyage, four days after the card was written. It sank in the early hours of 15 April, with around 1,500 lives lost.
As the ship went down, 25-year-old Phillips sent wireless messages enlisting other ships to assist with rescuing passengers and crew.
Auctioneer Andrew Aldridge, of Henry Aldridge and Son Ltd in Devizes, Wiltshire, described Phillips as “one of the true heroes of the disaster”.
Mr Aldridge said: "After abandoning ship when water flooded around his feet, he ended up on an overturned collapsible lifeboat where he later died of exposure to the severe cold.
"Harold Bride, the Titanic's junior wireless operator, always remembered Phillips as ‘the man who saved us all’.
"During his career, Phillips kept in frequent touch with his sister, Elsie.
"This card, however, holds particular significance as it was written on April 6, 1912 while Titanic was docked in Southampton, and contains an image of the ship.
“Quite simply one of the rarest postcards of its type in existence.”
The card is addressed to Miss Elsie Phillips of Godalming, Surrey, and shows a photo of the Titanic at Southampton.
It reads: “Thanks very much for your letter. Having glorious weather, went to Cowes yesterday. Will write later before we sail.”
Mr Aldridge said the postcard was estimated to fetch between £15,000 and £20,000 at auction.
He described its condition as “very good to fine”, noting some light soiling and toning, a date stamp over a couple of letters of text, a few light bends and corner tip bumps.
The photograph side has postal impressions, some light silvering and rubbing, and creasing to the lower right side.
The sale takes place at Henry Aldridge and Son on 21 November.
Read MoreWorld’s largest military airshow announces move to Boscombe Down
Henry Nowak’s family speak on ‘unbelievable pain’ after student’s murder
Treasury accepts that it contributed to staffer's death after inquest