11.35 Public Health: Water Fit to Drink?
Much of our drinking water comes from rivers. To maintain river quality, the Welsh Water Authority have to monitor it closely.

12.0 Statistics: Conflict
Doubling the size of a navy doesn't just double its effectiveness - it quadruples it. This is 'Lanchester's Square Law', discovered in 1914, but justified a century earlier at the Battle of Trafalgar.

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