A plan of the doomed liner Titanic sold for £220,000 at a Devizes auction on Saturday – twice its estimate.

The huge drawing, which was used at the public inquiry into the 1912 sinking of the ‘unsinkable’ liner, was expected to fetch between £100,000 and £120,000.

But when auctioneer Alan Aldridge brought down the hammer on the unique item, it is thought to have become the single most valuable artefact connected with the disaster.

The plan was bought by a private buyer, whose name has not been given, but who may exhibit it in future.

The day before the auction, children from All Cannings Primary School visited Aldridge’s auction rooms at Bath Road Business Centre to see the plan.

The 32ft by 5ft profile of the vessel was created to help 96 witnesses give testimony at the British British Board of Trade inquiry immediately after the disaster.

The gashes in the hull caused by the iceberg are clearly marked on the chart.

Andrew Aldridge, who is a noted expert on Titanic memorabilia and has been retained as an authority on the subject by BBC’s Antiques Roadshow, said: “The captain changed course when the iceberg was spotted but not soon enough to avoid the collision.

“If he had kept his course and hit the iceberg head on, the damage would have been much less and it is doubtful the ship would have sunk.”

Because the ship was unsinkable, the Board of Trade allowed the owners, the White Star Line, to leave port without enough lifeboats for all the passengers and crew. The owners felt that the lifeboats disfigured the handsome outline of the ship.