Of all the seafaring stories linked to Southampton there is one that will never die as generation after generation continues to be fascinated by the ill-fated Titanic.

The details of the "unsinkable'' Titanic, lost beneath the Atlantic waves on her maiden voyage between Southampton and New York after hitting an iceberg in 1912, have grabbed people's imagination for nine decades and will continue to do so far into the 21st century.

Over the years films and countless books have examined every aspect of Titanic but two authors and Titanic enthusiasts are convinced that all these works have got it wrong.

In Robert McDougall's and Robin Gardiner's latest book on the ship the controversial theory it was not Titanic that sank but her slightly older and almost identical sister ship, Olympic is again put forward.

The authors say this was as the result of the orders of the White Star Line following a collision in September 1911, between Olympic and the Royal Navy's armoured cruiser, HMS Hawke, in which both vessels were seriously damaged.

The hypothesis is contained in their book, Titanic, In Picture Postcards, a pictorial biography, which traces the ship's history from the Belfast shipbuilders yard, to her departure from Southamp-ton and the terrible loss of more than 1,500 lives when she foundered.

Both authors suggest that during the time Olympic was out of action the White Star Line lost huge amounts of money in repair bills and lost fares.

"At the end of the two-month repair Olympic was still not fit to resume her duties but with her at the builders was the almost complete Titanic,'' they say.

"What more natural course of action could there be, in an effort to recoup some of their lost earnings, than to send the untested Titanic to sea in her sister's place? Having once allowed Titanic to take Olympic's place, the owners were left with a seriously damaged ship that they had somehow to pass off as new."

The authors say that having decided to dispose of Olympic, as Titanic, the owners and the shipyard needed a plan.

"Olympic, as Titanic, would be sailed out into the middle of the Atlantic Ocean as if on a normal voyage. Once in the deepest water available, they would simulate a collision with an iceberg.

"All the people on board the liner would be taken off by other vessels which would be in the area, standing by.

"Then the sea-cocks of the liner would be opened and she would quietly sink. Had the plan worked, the name of Titanic would now be long forgotten, but the plan did not work.''

The authors believe everything went well until the night of April 14, 1912 when soon after 11pm, there was a collision.

"Instead of just pretending, Titanic really was sinking, and she was not where the pre-arranged rescue ships expected to find her, nor was she sinking at the time they expected to go to the rescue of those aboard.''

Robin Gardiner has previously written at length about the theory in his earlier book, Titanic: The Ship That Never Sank?

Titanic, In Picture Postcards by Robert McDougall and Robin Gardiner is published by Ian Allan at £19.99.

- Originally published August 2002.