Long-lost treasure from a ship that sank off Chesil Beach more than 250 years ago is to go under the hammer.

When the Dutch vessel Hope sank in 1749 she was laden with gold, silver and other treasures which are worth more than £4 million today.

The precise location of the wreck remains unknown, although it is thought by some experts to be off the Fleet, and the area attracts treasure hunters hoping to get rich.

Plumber Trevor Lee, 57, was diving off of the shingle bank hoping to find some sign of the wreck when he spotted part of a tusk poking out of the sand.

The 18th century elephant tusk he found is thought to be treasure from the Hope and on November 28 it will go under the hammer at Duke’s auction house in Dorchester with an estimate of £400.

Mr Lee said: “I was searching the general area of the wreck and I saw about three inches of the tusk exposed – I didn’t know what it was then but when I started to wiggle it about the other end moved and I could tell what it was.

“I stuck some air bags on it and we got it out – it’s certainly one of the strangest things I’ve ever found.”

He added: “The Hope was a treasure ship with gold and silver and lots of people dive in the area trying to find treasure.

“I got lucky and found the Pandora’s Box – the Hope.

“I have searched the area since but haven’t found anything else.”

Matthew Denney, of Duke’s, said: “The lure and romance of buried treasure is one that we are all familiar with.

“And this most unusual item is full of history bringing to life so vividly the story of the wreck of the Hope.”

When the ship sank in 1749 more than 2,000 looters flocked to the area to try and salvage any washed-up goods.