Martin McGuinness, seen here arriving at 10 Downing Street in central London last October for meetings in his role as Northern Ireland's deputy first minister, has died at age 66. Daniel Leal-Olivas/AFP/Getty Images hide caption

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Daniel Leal-Olivas/AFP/Getty Images

Queen Elizabeth II shook hands with Deputy First Minister of Northern Ireland Martin McGuinness today in Belfast. McGuinness is a former senior member of the IRA. Paul Faith/WPA Pool/Getty Images hide caption

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Paul Faith/WPA Pool/Getty Images