An injured protestor is led away during clashes with police near Tahrir Square on November 23, 2011 in Cairo, Egypt. Thousands of Egyptians are continuing to occupy Tahrir Square after four days of clashes with security forces despite a promise from military leaders to bring forward Presidential elections. (Photo by Peter Macdiarmid/Getty Images)

A simulated casualty is evacuated during an emergency services exercise at the disused Aldwych underground station on February 22, 2012 in London, England. Operation Forward Defensive aims to test the response to a terrorist incident on the London Underground network during the 2012 Olympic Games. (Photo by Peter Macdiarmid/Getty Images)

A girl allows a butterfly to be placed on her nose at the Sensational Butterflies exhibition at the Natural History Museum on April 6, 2011 in London, England. The exhibition is divided up into five sensory zones exploring how butterflies see, hear, taste, smell and touch. The display containing hundreds of butterflies runs from April 12 to September 11, 2011. (Photo by Peter Macdiarmid/Getty Images)

Tourist Police sit in the shade on a road leading to the Coptic Cairo area on May 27, 2011 in Cairo, Egypt. Protests in January and February brought an end to 30 years of autocratic rule by President Hosni Mubarak who will now face trial. Food prices have doubled and youth unemployment stands at 30%. Tourism is yet to return to pre-uprising levels. (Photo by Peter Macdiarmid/Getty Images)

A Banksy decorated truck entitled “Laugh now but one day we'll be in charge” is displayed for sale on October 6, 2011 in London, England. The Volvo FL6 lorry was decorated by British street artist Banksy for a millennium party for Turbozone, pyrotechnic touring circus. It will be offered for auction in London this month. (Photo by Peter Macdiarmid/Getty Images)

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)

Artist Ted Harrison makes final adjustments to his artwork created with poppies on the floor of St. Paul's Cathedral on November 10, 2011 in London, England. Mr. Harrison created the work on a 30 foot disc under the main dome of the cathedral with the intention of drawing attention to the 250,000 children worldwide currently under military orders. (Photo by Peter Macdiarmid/Getty Images)

Passengers ride an articulated bus known as a “bendy bus” on December 9, 2011 in London, England. The last remaining bendy bus will go out of service at midnight. London Mayor Boris Johnson called them cumbersome and pledged to remove them. 500 new buses are being introduced as replacements. (Photo by Peter Macdiarmid/Getty Images)