The only known surviving letter written by a passenger on the Titanic the day it sank is expected to fetch tens of thousands of dollars at auction.

The Henry Aldridge and Son auction house says the letter penned by Esther Hart, who survived the sinking with her seven-year-old daughter Eva, will go under the hammer April 26.

Survivor Esther Hart wrote the letter to her mother in Chadwell Heath, East London, but it was never sent. The letter was found in her husband's jacket after she and her seven-year-old daughter, Eva, were rescued.

Her husband, Benjamin, was one of more than 1,500 people who died in the maritime disaster.

The letter is due to be auctioned by Henry Aldridge & Son of Devizes, Wiltshire in England next month.

Auctioneer Andrew Aldridge said the importance of the letter could not be overstated, as it is "the only known surviving example of its type to have been written on that fateful day, surviving the sinking, and having belonged to such a well-known survivor."
    
The paper is headed "On Board RMS Titanic" and dated "Sunday afternoon." In it Hart describes being sick the day before and unable to eat or drink.

She said she had since recovered and had been to a church service with her daughter Eva that morning, on Sunday, 14 April.

She wrote that daughter Eva had sung "so nicely" to the hymn 'Oh God Our Help In Ages Past' and they were both due to sing in a concert on board "tomorrow night."

Remarking on the stability of the ship, which was not supposed to roll, Hart wrote: "Anyhow it rolls enough for me."

She added, "Well, the sailors say we have had a wonderful passage up to now."

Aldridge added, “The importance of this legendary item cannot be overstated, being the only known surviving example of its type to have been written on that fateful day, surviving the sinking, and having belonged to such a well-known survivor.”

Hart and her seven-year-old daughter, Eva, were among those rescued from the lifeboats.

Eva lived until 1996 and became one of the most-celebrated of the Titanic survivors.

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