In the 1840s, a speculative frenzy wiped out the savings of Britain’s middle class and, almost by accident, left behind the greatest railway network the world had seen. The Liverpool and Manchester Railway had proved the technology in 1830, but high interest rates kept money parked in government bonds for more than a decade. Then the Bank of England cut rates, the Bubble Act was gone, joint stock companies limited what an investor could lose, and promoters let ordinary clerks secure a 100 pound share with a 10 pound deposit.

This episode walks through the mechanics of the mania: Parliament passing 263 railway acts in 1846 alone while its own members held shares in the companies they approved, and George Hudson, the Railway King, paying dividends out of new investors’ capital. When rates rose in late 1845 the money dried up and deposits were wiped out. Yet the crash left iron in the ground, and the same pattern returned with the fiber optic overbuild of the 1990s and the race to build AI data centers.

• The 1846 acts proposed 9,500 miles of new track, and about a third of those miles were never built.
• George Hudson amalgamated smaller lines across the North and Midlands, but his empire evaporated once auditors opened his books.
• Survivors like the Great Western Railway bought half finished lines from bankrupt companies for pennies on the pound, gaining strategic links and blocking rivals.
• The lines authorized between 1844 and 1846 added 6,220 miles of railway, more than half the size of the modern UK network of around 11,000 miles.
• In the 1990s telecom companies leased railway rights of way to bury fiber optic cable, and after the crash Google and Amazon bought the unused dark fiber cheaply.