The Leukos was built in Aberdeen in 1914 at the John Duthie Torry shipyard - a coal-fired steam trawler ordered by the National Steam Fishing Company. During the First World War the Admiralty took her up as a boom defence vessel, maintaining the buoys and netting that kept German U-boats out of British harbours. She returned to fishing in 1920, changed owners, then in 1927 was sold to the Dublin Trawlers, Ice and Cold Storage Company and transferred to the Irish register. Her base became Hanover Quay in Ringsend, on the south bank of the Liffey, where her crew lived among the dockworkers and seamen of one of Dublin's oldest maritime neighbourhoods. By 1940 she was 26 years old, slow, unarmed, and painted with the conspicuous markings that international law required of neutral ships in wartime.

She sailed from Hanover Quay on 9 February 1940 under Captain James Potter Thomasson, called at Troon in Scotland for coal, then steamed north for the fishing ground the trawlermen called simply 'the bank' - rich waters northwest of Tory Island where the Atlantic shelves before dropping into the deep. Her companions that night were a mixed group: the British trawlers John Morris, Alvis, Pelagos, Flying Admiral, and Seddock. The Alvis and Pelagos carried 3-pounder guns mounted aft - the Admiralty had begun arming fishing boats against U-boat attacks. The Leukos carried no weapons at all. She trusted the tricolour painted on her hull to do the work that guns would have done for someone else.

Kapitanleutnant Heinrich Liebe's war diary describes what he saw: six steamers running with lights, apparently forming a guard line on a north-south course. He surfaced at 20:00 and waited, on the surface, for over an hour - nobody knows why. At 21:13 he fired a single round from U-38's deck gun at one of the trawlers. The shell hit the engine room at 200 metres. The steamer disappeared in smoke and dust. Liebe noted later in his log that the ship had not, he thought, actually sunk - some of the other trawlers, he wrote, 'seemed not to have noticed the gunfire.' The U-boat slipped back beneath the waves. None of the other boats came under attack. None of them ever saw the Leukos again.

She was due back in Dublin on 12 March. She did not come. On 21 March her empty lifeboat washed up off Scarinish on the Isle of Tiree in the Inner Hebrides, 200 miles from where she had been working. Five days later Lloyd's of London declared the Leukos and her eleven crew presumed lost. The official cause was unknown - possibly a mine, possibly structural failure from her 1927 collision, possibly anything at all. The Irish government had no way to investigate a sinking in disputed waters during wartime. The families in Dublin and Fleetwood and Donegal were told their men had been lost at sea. No death certificates were issued. The case sat closed for forty-six years.

Peter Mulvany was the grand-nephew of Patricio McCarthy, one of the lost crew. He spent years tracking down former U-boat personnel and reading declassified British intelligence files - Ultra intercepts of encrypted German radio traffic that had finally been opened to researchers. In 1986 the death certificates were finally issued. In 1987 Mulvany published his findings in the Journal of the Maritime Institute of Ireland. The U-38 had killed the Leukos. Why she had killed the only neutral ship in the group while leaving five British trawlers untouched - including two that were armed - Liebe never said. Asked to comment in 1988, he declined. He died in 1997, taking the answer with him. The Irish Seamen's Relatives Association believes the Leukos placed herself deliberately between the U-boat and the British boats, betting that her tricolour would shield them. The evidence is consistent with that theory. It is not conclusive. What is certain is that eleven men died in cold March water off the Donegal coast, and that their names are remembered on Hanover Quay where their ship once tied up.