IT could be the most expensive bookmark in history.

A letter from a passenger on board Titanic is expected to raise up to £20,000 when it goes under the hammer next month.

The true worth of the folded A4 piece of paper only came to light when Christian Duff - who used it as a bookmark - made a chance remark to a valuer.

It was sent to her father by first-class passenger Alice Lennox-Conyngham and was part of the last consignment of mail sent out from the liner before it set out from Ireland to the Atlantic.

Miss Lennox-Conyngham wrote of the moment the vessel nearly collided with a tug as she departed Southampton Docks.

She sailed only on the first leg of the cruise from the city to Cherbourg in France.

Diane Sinnott, of Tennants auctioneers, said Miss Duff, from Darlington, had been completely unaware of the letter's worth.

She said: "It still has its original envelope with its stamp and postal cancellation marks on it.

"It's also got good provenance."

It will be auctioned on February 25 in north Yorkshire.

- Originally published January 2004.