The letter which was written on board the Titanic

The letter, which was used as a bookmark for years, was written on the White Star Line RMS Titanic headed notepaper.

The folded piece of A4 paper, complete with its original envelope, is to be auctioned by Tennants of Leyburn, in North Yorkshire, and contains the letter written by first class passenger Miss Alice Lennox-Conyngham.

It was part of the last consignment of mail from the Titanic, which was built at the Harland & Wolff shipyard in Belfast, before it set out from Queenstown in the Republic of Ireland to cross the North Atlantic, where it sank after hitting an iceberg.

Miss Lennox-Conyngham, who sailed on the first leg of the cruise from Southampton to Cherbourg in France, wrote to her nephew Master Alan C Duff to say the liner had narrowly avoided a collision even before it left Southampton.

"There was nearly an accident just as we started but we did not know till it was nearly over," she wrote.

'Luxurious liner'

"It is a vast place - five decks, immense drawing rooms, dining rooms and swimming baths and gymnasium - and a band playing."

The letter even mentions that the weather was chilly.

"It's rather cold but not too bad," it says.

The letter, dated 10 April 1912, is being put up for sale by its owner, Master Alan's daughter Christian Duff, who lives near Darlington.

It was postmarked a day later, just three days before the liner hit the iceberg and sank on April 14.

Miss Duff was unaware of its potential value until a chance remark she made to Tennants valuer Diane Sinnott.

Ms Sinnott, who recognised the worth of the letter, said: "The lady had no idea it was worth anything and it was being used as a bookmark.

"It still has its original envelope, with its stamp and postal cancellation marks on it. It's also got good provenance.

"It has everything you could possibly want. It even mentions the weather being chilly."

Ms Sinnott said the letter was valued at £6,000 - £8,000, but could fetch up to £20,000 in the sale.

She said there had already been a keen interest from potential bidders.

Collections of items from the Titanic are extremely popular at the moment, particularly with collectors in New York and Australia, Ms Sinnott said.