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A protester demonstrates outside Downing Street in central London on March 3, 2015 over the abduction of 43 students in Mexico over four months ago, on the first day of Mexican President Enrique Pena Nieto's state visit to Britain. Mexico has faced international outrage and regular protests over the disappearance and alleged slaughter of 43 college students at the hands of a police-backed gang in September. The visit to Britain holds significant diplomatic importance for Pena Nieto, who is struggling with falling approval ratings and relentless drug violence at home. AFP PHOTO / JACK TAYLOR (Photo credit should read JACK TAYLOR/AFP via Getty Images)