Water detective Dr Leon Barron studies London’s wastewater, analysing it in all its chemical, narcotic, polluted glory, before and after treatment. Amazingly, he still drinks the stuff from the tap

If you live in London, Dr Leon Barron knows what you’re up to. He knows what prescribed drugs you’re on – painkillers, antidepressants, antipsychotics or beta blockers – and what illicit ones you’re taking for fun. He knows if you’ve been drinking and when (“Friday and Saturday are the main ones”); perhaps even if you’re worried about your dog getting fleas.