John Snow, 19-century physician and founding father of the modern science of epidemiology, is best known for his work with cholera. The scourge of Victorian Britain, cholera struck four times in the 1800s, subjecting tens of thousands to an exceptionally unpleasant death, the details of which even today make for difficult reading.

While clearly the evidence pointed to a link with filthy living conditions, cholera was unpredictable and indiscriminate, such that no one could work out exactly how it was transmitted.

Snow's suspicion that cross-contamination between sewerage and water supply lay at the heart of the matter was confirmed during a particularly virulent outbreak in Soho, when hundreds were struck down almost overnight.

Snow implored the local guardians to remove the handle from the water pump on Broad Street, as a result of which the outbreak was quickly arrested.

But Hempel does much more than retell a story that has passed into scientific legend. Delving into Snow's background, we discover a reserved but deeply compassionate man, who also turns out to have been a pioneer of anaesthesia.

Even the Broad Street story as frequently told is less than complete, Snow having already gathered ample evidence elsewhere in London by comparing the death rates from cholera applicable to the customers of two competing private water companies (anyone with a gripe against Thames Water, take note).

So next time you're in London, take a stroll down Broad Street now Broadwick Street and visit the John Snow' pub. If you fancy drinking a toast to the good doctor, the site of the original pump is marked on the pavement just outside. A glass of tap water would seem appropriate.