The boiling kettle story is a myth, likely manufactured by his own son as a 19th-century PR campaign. James Watt did not invent the steam engine and was never struck by kitchen-table lightning. What he actually did was harder and far more interesting: he diagnosed why the existing Newcomen engine wasted three-quarters of its energy reheating its own cylinder, and hacked it to be five times better, accidentally creating the mechanical workhorse of the Industrial Revolution.

This episode follows a sickly, chronically anxious Scottish instrument maker who was locked out of his own profession by the guilds, snuck in through a university back door, and absorbed the Scottish Enlightenment alongside Joseph Black and Adam Smith. It covers the separate condenser insight built on latent heat theory, the decade of broke and leaking prototypes, the partnership with Matthew Boulton that saved it all, and the locked attic workshop preserved as a shrine that you can still visit today.

• The kettle myth versus the real story: why we keep inventing eureka moments for grinding work
• The rogue campus repairman: how a dead merchant's telescopes got Watt past the Glasgow guilds
• Boiling water in a pot made of ice: the Newcomen engine's fatal thermodynamic flaw
• Latent heat, the separate condenser, and the Boulton partnership that turned theory into an empire
• Horsepower as a marketing gimmick, the watt on your light bulb, and the attic shrine in the Science Museum