A Lynx helicopter hovers over a commuter boat during a combined British police and British Royal Marines security exercise on the River Thames, London, Thursday, Jan. 19, 2012. British

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A Lynx helicopter hovers over a commuter boat during a combined British police and British Royal Marines security exercise on the River Thames, London, Thursday, Jan. 19, 2012. British police and military forces using a helicopter and inflatable boats teamed up Thursday to practice security procedures designed to protect the Thames river from possible terrorist attack during the 2012 London Olympics. (AP Photo/Kirsty Wigglesworth) less