Racegoers during Ladies Day of the 2018 Cheltenham Festival in Cheltenham, England on March 14, 2018. (Photo by Graham Stone/Rex Features/Shutterstock)

A demonstrator shows her arm with the name “Marielle” written on it, as she performs during a protest against the murder of councilwoman Marielle Franco in Rio de Janeiro, Brazil, Tuesday, March 20, 2018. Franco's murder came just a month after the government put the military in charge of security in Rio, which is experiencing a sharp spike in violence less than two years after hosting the 2016 Summer Olympics. (Photo by Leo Correa/AP Photo)

South Vietnamese forces escort suspected Viet Cong officer Nguyen Van Lem (also known as Bay Lop) on a Saigon street February 1, 1968, early in the Tet Offensive. Moments later, Lem was executed by Gen. Nguyen Ngoc Loan, chief of the national police. (Photo by Eddie Adams/AP Photo)

Starlings are seen at their nesting box in a private garden in the town of Bobruisk, Belarus, April 8, 2018. (Photo by Vasily Fedosenko/Reuters)

Children in a Hong Kong refugee resettlement area watch as former Vice President Richard Nixon shows them his badminton service. Nixon visited Hong Kong, April 4, 1964, during his tour of countries in the Far East. (Photo by AP Photo)

An OV-10 Bronco aircraft, decorated with World War One commemoration motifs, flies over Flanders international airport, ahead of the world's first Short Take Off & Landing competition on sand, in Wevelgem, Belgium May 8, 2018. (Photo by Francois Lenoir/Reuters)

The social media star, British model Demi Rose wows her fans and showed off her famous curves as she modelled in a bikini for “I Saw It First” in Ibiza, Spain on Monday, May 28, 2018. (Photo by KP Pictures)

Prince Philip, Duke of Edinburgh practicing his bicycle polo technique, Windsor Great Park, Berkshire, 1964. (Photo by Norman Potter/Daily Express/Hulton Archive/Getty Images)