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)

In this handout image supplied by the Olympic Delivery Authority, workers carryout the installation of artist Monica Bonvicini's “RUN” sculpture in the plaza of the London 2012 Handball Arena at the Olympic Park on January 12, 2012 in London, England. (Photo by Olympic Delivery Authority via Getty Images)

International film actress Gillian Anderson pictured on the rooftop of the Ritz-Carlton Hotel overlooking Red Square in a British Airways Business Class seat to launch the British Airways long haul service on the London – Moscow route on March 6, 2012 in Moscow, Russia. (Photo by Gareth Cattermole/Getty Images For British Airways)

Emergency services work at the scene of a bus accident on the Kingsway in central London February 2, 2015. A number 91 double-decker bus had its roof ripped off after hitting a tree, causing injury to passengers and passers-by, local media reported. (Photo by Peter Nicholls/Reuters)

A five-month-old female slender loris waits to be given her first health check by the veterinary team at London Zoo on July 21, 2011 in London, England. Two female baby slender lorises, who are yet to be named, were given health checks, their s*x determined and micro-chipped. Slender Loris is the common name for the strepsirrhine primates who are nocturnal and originate from India, Sri Lanka, and southeast Asia. London Zoo supports conservation of lorises in Sri Lanka, where populations are thought to be under threat from deforestation. (Photo by Christopher Furlong/Getty Images)

Alejandro Simon of Spain prepares to serve during their Preliminary Phase Pool E match against Canada during the VISA FIVB Beach Volleyball International at Horse Guards Parade on August 10, 2011 in London, England. (Photo by Scott Heavey/Getty Images)

Models walk the runway at the “A Child of the Jago” fashion show during London Fashion Week at the Wilton Music Hall on September 21, 2011 in London, United Kingdom. (Photo by Ian Gavan/Getty Images)