Medals belonging to a man who "may have unwittingly caused the Titanic to sink" are to be sold.
David Blair forgot to hand over a key to a crow's nest locker containing binoculars when he was taken off the ill-fated liner at the last minute.
The doomed steamer famously hit an iceberg on its maiden voyage across the Atlantic.
Murray Shaw, who owns the medals, said Mr Blair could have helped steer the ship to safety.
The retired teacher, from Derby, said Mr Blair sailed on the Titanic from Belfast to Southampton, but was "surplus to requirements".
"He would have been responsible for all the navigation equipment," he said.
"As a former Navy man myself, I can understand why he would have been upset."
Born in Broughty Ferry, Dundee, Mr Blair sailed on the Titanic on 3 April 1912.
Having been involved in trials to test the Titanic's seaworthiness, he was set to be second officer for the maiden voyage to New York, but White Star Line, the ship's owners, drafted in Henry Wilde from sister ship The Olympic because of his experience of large liners.
However, the locker key was not handed over, and the binoculars it contained could have been used by the ship's crew to look out for hazards.
Mr Wilde was one of more than 1,500 people who died when the Titanic struck the iceberg in the early hours of 15 April.
Mr Blair, who died aged 80 in 1955, was later awarded the King's Gallantry medal for jumping into the Atlantic to rescue a crewman.
Among other medals he received were a British Empire Medal, a French Cross of Chevalier of the Legion of Honour, a Royal Naval Reserve Decoration, and an OBE.
The items will be auctioned on 19 March by Hansons Auctioneers at Etwall, Derbyshire.
The key to the locker was itself sold at an auction for £90,000 in 2007.
Adrian Stevenson, militaria expert for Hansons, said Mr Blair's items helped to tell "a fascinating story".
"It's astonishing to think that Mr Blair may have unwittingly caused the Titanic to sink by simply forgetting to hand in a key," he said.