A female motorcycle cop directs traffic wearing crash helmet, Haywarket Square, Boston, Massachusetts, 1979. (Photo by Spencer Grant/Getty Images)

Members of the Hitler Youth who are trained to report airstrikes repaining their bicycles. Published by: “Die Sirene”. 1942. (Photo by Herbert Hoffmann/Ullstein Bild via Getty Images)

An actor plays an injured passer-by during Exercise Strong Tower, the scene of a mock terror attack at a disused underground station in central London, Britain June 30, 2015. London police held their biggest-ever terrorism drill on Tuesday, pitting the emergency services against a group of marauding attackers, nearly 10 years since four young British Islamists killed 52 people in suicide bombings on London's transport network in July 2005. (Photo by Peter Nicholls/Reuters)

A man poses as “Lemongrab” from Adventure Time outside the MCM Comic Con at the Excel Centre in East London, October 25, 2014. (Photo by Andrew Winning/Reuters)

Musician “Girli” poses for a portrait during London Fashion Week in London, Britain February 21, 2017. (Photo by Neil Hall/Reuters)

Nic Smith poses to show her body art during the 10th International Tattoo Convention in London September 27, 2014. (Photo by Neil Hall/Reuters)

A man inspects a plastic cover placed over an artwork attributed to Banksy on May 17, 2012 in London, England. The stencilled image depicts a poor child making Union Jack flags on a sewing machine and is located on the wall of a Poundland discount shop in the Wood Green area of north London. (Photo by Peter Macdiarmid)