The first Tay Bridge had opened just nineteen months earlier, on 1 June 1878. Its designer, Thomas Bouch, had been knighted for the achievement. Queen Victoria herself had crossed it in June 1879. The bridge was a marvel of its age: over two miles of lattice ironwork spanning a major estuary, carrying a single railway track from Wormit in Fife to Dundee. But the design had been compromised from the start. When trial borings revealed that the bedrock lay far deeper than expected, Bouch redesigned the bridge with fewer piers and longer spans, resting not on rock but on gravel that had been misidentified as a solid foundation. The cast-iron columns of the high girders were braced with wrought-iron ties that a witness at the subsequent inquiry described as "about as slovenly a piece of work as ever I saw in my life." The bridge had never been tested for wind loading.

By 7:15 p.m. on that December Sunday, a gale estimated at force ten or eleven was blowing down the Tay estuary at right angles to the bridge. The 5:20 train from Burntisland, running late, had entered the high girders section. From the signal box at the south end of the bridge, the signalman watched the tail-lights of the train disappear into the darkness and the driving rain. Then he saw sparks -- a cascade of them, falling toward the water. Then nothing. The central spans, all thirteen of them, had collapsed into the firth, taking the train and its passengers with them. The disaster stunned Victorian Britain. The ensuing Court of Inquiry determined that the bridge had been insufficiently engineered to withstand high winds, exposing failures of design, construction, and inspection that would reshape how bridges were built across the British Empire.

The locomotive, North British Railway no. 224, was salvaged from the riverbed. A 4-4-0 designed by Thomas Wheatley and built at Cowlairs Works in 1871, she was repaired and returned to service, remaining on the railway until 1919. Drivers nicknamed her "The Diver," and many were superstitious about taking her across the new bridge that replaced the original. The disaster also produced one of the most famous bad poems in the English language. William McGonagall's "The Tay Bridge Disaster" is widely considered so poorly written as to be unintentionally comic, its earnest doggerel a strange counterpoint to the tragedy it commemorates. The German poet Theodor Fontane, by contrast, responded with a poem of genuine literary merit, published just ten days after the collapse.

Thomas Bouch did not survive his bridge's failure by long. Already ill, he died in October 1880, ten months after the disaster. His reputation was destroyed, and investigations into his other structures revealed further problems: the South Esk viaduct was found unsafe and had to be rebuilt, and his Redheugh Bridge was condemned in 1896. Some in the Sabbatarian movement pointed to the disaster as divine punishment for Sunday travel -- a minister of the Free Church of Scotland criticised the victims for "transgressing the Law of God." Memorials now stand at both ends of the current bridge, in Dundee and Wormit. On 28 December 2019, Dundee Waterfronts Walks hosted a remembrance walk marking the 140th anniversary of the disaster. The broken piers remain visible at low and high tide alike, a reminder that ambition without rigour carries a cost measured in lives.