The expression ‘to get a handle on something’ has perhaps never had a more literal example.
Long long before the Game of Thrones character or the England fast bowler, there was another John Snow, and this one probably saved many lives.
John Snow (15 March 1813 – 16 June 1858) and the infamous water pump.
Design by Accent Studio.
In 1854 over 600 people died when a cholera epidemic swept London. It looked like that number was going to increase massively when physician John Snow identified an unassuming water pump on Broadwick St. as the cause of the outbreak.

Snow was convinced that cholera was spread through the consumption of contaminated water but was struggling to convince his peers and other scientists.  So, using none of his medical and physician skills whatsoever, he went to the Broadwick Street water pump and simply removed the handle. Hey presto, cases of cholera declined and the outbreak subsided.

The pump can still bee seen in its original location and the city remains free of cholera!