A frame grab from a video released by the Islamic State shows an IS militant holding a knife before purportedly executing British aid worker David Cawthorne Haines. Islamic State Video/EPA /LANDOV hide caption

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The prime minister's "red box," looking rather lonely, on a train Saturday from London to York. The Mirror made it front page news. The Mirror hide caption

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British Prime Minister David Cameron, who says it is time for the U.N. Security Council "to live up to its responsibilities on Syria." Stefan Wermuth /Reuters /Landov hide caption

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British Prime Minister David Cameron has announced plans to block Internet porn by default on all British computers. Getty Images hide caption

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The G-8 leaders speaking at this news conference in Northern Ireland all lost their ties, but British Prime Minister David Cameron (right) went a step further by ditching his jacket and rolling up his sleeves. Andrew Winning/WPA Pool/Getty Images hide caption

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The victim: Drummer Lee Rigby. U.K. Ministry of Defense hide caption

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President Obama and British Prime Minister David Cameron in the Oval Office of the White House on Monday. Jim Watson /AFP/Getty Images hide caption

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British Prime Minister David Cameron (left) and Russian President Vladimir Putin viewed the Sochi Olympic Park along the Black Sea coast by helicopter Friday. Nikolsky Alexei /ITAR-TASS /Landov hide caption

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A rebel fighter raises his weapon after firing a missile Sunday toward Syrian government troops in the northern city of Aleppo. Syria's largest city has been the scene of heavy fighting for the past three months. Both sides control part of the city, and the fight has been a stalemate recently. Narciso Contreras/AP hide caption

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