Charlie Chaplin's contributions to the eighth art are indisputable. His most famous character, The Tramp, entertained millions and has influenced both "serious" actors and physical comedians for almost 100 years. But it doesn't take a film scholar to see that many of Chaplin's films contain pro-socialist messages, especially in those that he directed. In 1952 during the House Committee on Un-American Activities's second series of investigations, Chaplin was denied re-entry to the U.S. Chaplin lived the rest of his life in Europe, and obtained a knighthood in 1975 — despite a great deal of pressure from the F.B.I.

Iran says another one of its nuclear scientists has been killed, this time by a motorcyclist who attached a bomb to his car in Tehran this morning. It was the fourth such killing reported in two years and comes at a time of growing tension between Iran and the West. Joining the program is Gordon Corera, security correspondent for our partner the BBC.

Concerns over security at the 2012 Olympics has prompted the United States to send 1,000 agents, including 500 from the FBI, to provide protection for its athletes in London. The Guardian is reporting this morning that American officials are apprehensive over British anti-terrorism laws and the effectiveness of their police force to handle threats. Their British counterparts, however, are concerned about the U.S. operating outside its jurisdiction. Gordon Corera, the BBC's security correspondent, has the latest from London.

Serbia has sent 2.5 tons of its remaining nuclear waste, including highly-enriched uranium from a nuclear research facility near Belgrade, to a disposal site in Russia. The month-long secret operation was the largest single shipment made to return such nuclear material to the country where it originally came from. However, details of the route are classified to prevent terrorists from hijacking the cargo.