The replica of the grand staircase on the Titanic, from which Dr Bob Ballard spoke yesterday, was missing one of its embellishments.
A decorative bronze cherub was lost in limbo, its future threatened by a financial crisis.
It was Dr Ballard’s mission, he said, to bring it home to Britain.
The cherub is among some 5,500 artefacts recovered from the Titanic’s undersea grave over the course of seven expeditions between 1987 and 2004.
The others include the ship’s whistles, jewellery, luggage, porcelain dishes, floor tiles, silver cutlery and an unopened bottle of champagne.
The American company which owns them has filed for bankruptcy, and the fear that the collection will be broken up was what had brought Dr Ballard to Belfast, where Titanic was built.
There, in the museum dedicated to the ship and the more than 1,500 people who died on its maiden voyage in 1912, he launched a £14m appeal for their rescue.
Speaking from a podium half way up the oak staircase, one of several faithful replicas in the museum, he said: “I’m lending my voice to this campaign as it is the right thing to do.
“This bid is the only viable option to retain the integrity of the Titanic collection. The collection deserves to be returned home to where its journey began.”
Dr Ballard had discovered the wreck of Titanic in 1985, and he was joined via video link by James Cameron, the Hollywood director of the 1997 epic, who said he felt a “deep responsibility” to the ship.
“Once Titanic is in your life, it doesn’t leave easily,” said Mr Cameron, who has made 33 dives to its grave over a 10-year period.
“You feel responsible to get the story right and honour the dead and the tragedy,” he said.
“I went to the wreck site for a purpose, to film the Titanic for a movie but I came away with a sense of a greater purpose which is to tell that story by whatever means.”
The bid for the collection of artefacts, which also includes a 7x4m section of the ship’s hull, is a joint initiative by the Belfast museum, the Titanic Foundation, National Museums Northern Ireland and the National Maritime Museum.
Mr Cameron and Dr Ballard met museum executives at the American headquarters of the National Geographic Society a year ago. Following the meeting, the Society pledged $500,000 to help with fundraising.
Its chief executive, Michael Ulica, said: “The Titanic disaster was an unprecedented tragedy that captivated the world and still resonates with many people today. The repatriation of the shipwreck’s artefacts presents an historic opportunity to honour the Titanic’s legacy and the memories of all who perished.”
Mr Cameron, who observed that he had “spent more time on the ship than the captain did”, added: “One of the concerns is that the collection would be broken up, sold privately, the bankruptcy court might award the company the opportunity to break up the collection, to sell it piecemeal and it would disappear from the public eye.
“That’s why people who feel some responsibility around Titanic have stepped up.
“If it’s sold privately that would be wrong, it’s a part of the world heritage. It’s an incredible piece of history.”