A horse named Quinn, with a skeleton painted on it to help educate officers, is pictured during a visit by Britain's Queen Elizabeth II (unseen) and Britain's Prince Charles, Prince of Wales (unseen) to the Household Cavalry Mounted Regiment at the Hyde Park Barracks in west London on October 24, 2017. (Photo by Chris Jackson/AFP Photo)

Some of London's telephone operators and engineers, trying out their gas masks at the anti-gas civilian training centre in Gloucester, where they were taught how to deal with gas attacks. (Photo by Harry Todd/Fox Photos/Getty Images). 13th February 1937

A protester uses molotov cocktails against riot police during May Day protests on May 1, 2010 in Athens, Greece. (Photo by Milos Bicanski /Getty Images)

The moon shines through trees at a United Nations displacement camp at dusk on March 14, 2011 in Ras Jdir, Tunisia. (Photo by Dan Kitwood/Getty Images)

A demonstrator is detained during May Day rallies in Santiago May 1, 2013. (Photo by Ivan Alvarado/Reuters)

Coffins are lined up near the wreckage of the bus, on July 29, 2013. (Photo by Salvatore Laporta/Associated Press)

“Mountain Goats, Colorado”. A herd of mountain goats huddle together on top of Mount Evans, Colorado during a lightning storm. This photo was selected out of more than 5,000 entries to go on display in “Wilderness Forever: 50 Years of Protecting America’s Wild Places”, a new photo exhibition at the Smithsonian’s National Museum of Natural History, which will run through summer 2015. (Photo by Verdon Tomajko/Smithsonian Wilderness Forever Photo Contest)

Ryan Randall plays the bagpipes outside a polling station in Edinburgh, Scotland September 18, 2014. Polling in the referendum on Scottish independence began on Thursday morning, as Scotland votes whether or not to end the 307-year-old union with the rest of the United Kingdom. (Photo by Paul Hackett/Reuters)