New Orleans police officers try to keep their heads down as they move in on a Black Panther headquarters during an exchange of gunfire in New Orleans on September 15, 1970. The shootout occurred as police moved in to make arrests on Tuesday morning following a series of incidents. (Photo by Jack Thornell/AP Photo)

Furniture design “Chair” by Allen Jones ( £600,000-800,000) is seen at Christie's London on September 29, 2017 in London, England. Christie's Auction House is to sell millions of pounds worth of art and design from the 20th and 21st centuries during Frieze Week from October 3rd to October 7th. (Photo by Nils Jorgensen/Rex Features/Shutterstock)

The Lake of Lights at Talkin Tarn lake near Brampton in Cumbria, England on October 22, 2017 – where hundreds of lights in the surrounding woodland represent a cherished memory of a relative friend or loved one no longer with us. (Photo by Owen Humphreys/PA Images via Getty Images)

People wearing costumes walk during Halloween in Sierra Madre, California, U.S., October 31, 2017. (Photo by Mario Anzuoni/Reuters)

Yippie leader Jerry Rubin, barred on December 4, from House Un-American Activities subcommittee hearing, aims a toy gun in “self defense” outside the Washington hearing room on December 5, 1969. Rubin showed up in his Santa Clause suit because he believed it was typical of the committee which, he said, “is a total circus”. (Photo by Bob Daugherty/AP Photo)

People walk past stranded cargo ship “Ocean Crown” during a windy weather in Klaipeda, Lithuania on December 26, 2017. (Photo by Ints Kalnins/Reuters)

The homemade Airbus A320 jet plane made by Chinese farmer Zhu Yue is being built at an open space in Kaiyuan city, northeast China's Liaoning province on February 4, 2018. (Photo by Imaginechina/Rex Features/Shutterstock)

Leslie Cliff and his wife Violet, English figure skating pair. Olympic games of Garmisch-Partenkirchen (Germany), 1936. (Photo by Roger Viollet Collection/Getty Images)