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)

A clock showing a countdown to the start of the London 2012 Olympics is unveiled on March 14, 2011 in London, England. The clock is starting five hours from midnight when 6.6 million tickets for the Olympics will become available and 500 days before the Games start. There is a six-week window to apply for tickets on the London 2012 website.

Zookeepers measure the length of a pueblan milk snake in the Reptile House of ZSL London Zoo as part of their annual weighing and measuring of their animals on August 25, 2011 in London, England. The heights and weights of over 750 different animal species at the zoo are recorded into the International Species Information System, to monitor their health and share the data with other zoos across the world. (Photo by Oli Scarff/Getty Images)

A woman cartwheels through the Coachella Valley Music and Arts Festival in Indio, California April 10, 2015. (Photo by Lucy Nicholson/Reuters)

A police officer removes a reveler from standing on a post as they guard and clear the street of revelers dressed in holiday themed costumes during SantaCon in New York Saturday, December 12, 2015. As thousands of Santa-suited merrymakers prepare to hit the city's streets and bars, organizers of the annual pub crawl say they're taking more steps than ever to deter naughty behavior. (Photo by Andres Kudacki/AP Photo)

An actress dressed as Black Cat poses for a photo at the London Super Comic Convention at the ExCeL Centre on February 23, 2013 in London, England. Enthusiasts at the Comic Convention are encouraged to wear a costume of their favourite comic character and flock to the ExCeL to gather all the latest news in the world of comics, manga, anime, film, cosplay, games and cult fiction. (Photo by Jordan Mansfield)

The London 2012 ArcelorMittal Orbit Sculpture at the Olympic park nears completion on November 4, 2011 in London, England. The Ј22 million sculpture designed by Anish Kapoor is nearly complete. Standing at 115 meters tall the permanent structure is Britain's largest artwork and houses an observation deck near the top. (Photo by Peter Macdiarmid/Getty Images)