A member of the Eton public school O.T.C. (Officers Training Corps) practising shouting out orders during a training session, 20th January 1940. (Photo by Hulton Archive/Getty Images)

Traditional miners carry sulphur on the Ijen volcano complex on May 25, 2009 outside Banyuwangi, East Java, Indonesia. Miners carry the solidified yellow sulphur blocks from the crater floor to the rim for as many hours a day as they can tolerate, paid by the kilogram of sulphur they extract. The average wage is USD $.05 per kilogram of sulphur and a worker, depending on his strength and stamina, carry on average 3 baskets of 70-80kg per day, earning him around USD $11. (Photo by Ulet Ifansasti/Getty Images)

A couple ride a motorcycle along a street during snow in Altay, Xinjiang Uighur Autonomous Region, China, November 8, 2015. Picture taken November 8, 2015. (Photo by Reuters/Stringer)

A glass skywalk in Wanyuan, Sichuan province, built along the side of a cliff, is the highest such skywalk anywhere in China on January 31, 2017. Some visitors have been proven to be terrified by the experience had to brace against the wall in fear. (Photo by Chinanew.com/AsiaWire)

A roadside currency exchange vendor sorts Indian currency notes at his stall in Agartala, India, December 6, 2016. (Photo by Jayanta Dey/Reuters)

In this October 29, 2013 photo, Daniel smokes marijuana inside his apartment where he uses a hydroponics system to grow his weed in Mexico City. “I'm not a narco, dude. I just like to smoke”, said Daniel, who spoke on condition that his last name not be used because, he said, his home-grow operation is "super-illegal" despite being for personal use only. (Photo by Eduardo Verdugo/AP Photo)

In this September 16, 2017 photo, a music fan poses for the photo against an angel wings' mural at the Rock in Rio music festival in Rio de Janeiro, Brazil. (Photo by Leo Correa/AP Photo)

Against the scorching sun, a hungry jackal chases a flock of birds looking for a quick morning snack. Taken in South Africa's Kgalagadi Transfrontier National Park, these images capture the moment a lone hunter tries, and then succeeds, in his pursuit. (Photo by John Mullineux/Solent News)