Corporal of Horse Andy Radford prepares to mount his horse in the parade square at Hyde Park Barracks on April 15, 2011 in London, England. Members of the Household Cavalry gave a behind the scenes tour of many of the duties performed as part of their daily routine, including special preparation ahead of the forthcoming Royal Wedding. The Household Cavalry will perform several ceremonial duties during the summer, including the Royal Wedding on April 29, and the Queen's Birthday Parade (Trooping the Colour) in June. (Photo by Dan Kitwood/Getty Images)

A woman poses with a cut-out of Vladimir Putin in the “President Cafe” in Krasnoyarsk, Siberia, Russia, April 7, 2016. Dozens of photos of Vladimir Putin, from childhood to Russian President, hang on the walls of President Cafe in a working-class area of Krasnoyarsk, a city in eastern Siberia. A life-size cut-out of Putin stands by the bar. Images of U.S. President Barack Obama, as well as leaders of Germany and Britain, greet customers in the toilets. (Photo by Ilya Naymushin/Reuters)

Iraqi soldiers work at a radio station at Makhmour base, Iraq April 17, 2016. The Iraqi army has set up a radio station at its base in Makhmour broadcasting into areas south of Mosul controlled by Islamic State militants. The radio, which reaches villages halfway to the northern city, broadcasts military anthems and messages to the more than one million civilians living there. Radio operators said their aim was to weaken the militants’ morale and reassure civilians that the military has not forgotten them after nearly two years under Islamic State control. (Photo by Ahmed Jadallah/Reuters)

A native Brazilian competes in a tora competition, which is a race while carrying a log, during the Indigenous Youth Games of Pataxos nation in Santa Cruz de Cabralia, Bahia state, Brazil, April 18, 2016. (Photo by Roosevelt Cassio/Reuters)

A containment shelter for the damaged fourth reactor (L) and the New Safe Confinement (NSC) structure (R) at the Chernobyl Nuclear Power Plant are seen from Ukraine's abandoned town of Pripyat, Ukraine, April 22, 2016. (Photo by Gleb Garanich/Reuters)

Ukrainian teenagers hit each other with pillows during a large pillow fight in downtown Kiev, Ukraine, 24 April 2016. About hundred people took part in the event “Pillow battle 2016” in Kiev. (Photo by Roman Pilipey/EPA)

A wildlife ranger strokes a northern white rhino, only three of its kind left in the world, ahead of the Giant Club Summit of African leaders and others on tackling poaching of elephants and rhinos, Ol Pejeta conservancy near the town of Nanyuki, Laikipia County, Kenya, April 28, 2016. (Photo by Siegfried Modola/Reuters)

An undated handout picture made available on 29 April 2016 by the Toronga Zoo shows a baby echidna making a remarkable recovery after being attacked by chickens in a family's backyard at the Taronga Zoo in Sydney, Australia. (Photo by EPA/Taronga Zoo)