In June 1879, Thomas Bouch stood at the peak of Victorian engineering fame. He had just been knighted by Queen Victoria for designing the Tay Bridge — at nearly two miles long, the longest bridge in the world. Six months later, on a stormy December night, the central spans collapsed into the Firth of Tay while a train was crossing, killing all 75 people aboard.

This video unpacks one of the most consequential engineering failures of the 19th century. The Tay Bridge disaster wasn't just a tragedy — it fundamentally reshaped how engineers calculate wind loads on structures. Bouch had used a wind pressure estimate that was wildly inadequate for the exposed estuary, and the cast iron columns supporting the "high girders" were riddled with casting flaws hidden by cosmetic filler. The official inquiry became a landmark in engineering accountability.

What makes this worth watching is the arc: from national hero to disgraced figure in half a year, and the way the disaster forced a reckoning with the limits of Victorian confidence in iron. Bouch died broken less than a year after the collapse, and his design for the Forth Bridge was scrapped — the replacement is the famous cantilever structure still standing today. It's a compact case study in how catastrophic failure drives engineering progress.