A police officer with a dog patrols a central London train station on Monday, Oct. 4, 2010. Britain's Foreign Office has upgraded its travel advice for France and Germany, warning Britons going to those countries that the threat of terrorism there is high. British Home Secretary Theresa May said that the threat of terrorism in the United Kingdom remains unchanged at "severe," meaning an attack is highly likely. (AP Photo/Lefteris Pitarakis)

Photo by: Lefteris Pitarakis

A police officer with a dog patrols a central London train station on Monday, Oct. 4, 2010. Britain's Foreign Office has upgraded its travel advice for France and Germany, warning Britons going to those countries that the threat of terrorism there is high. British Home Secretary Theresa May said that the threat of terrorism in the United Kingdom remains unchanged at "severe," meaning an attack is highly likely. (AP Photo/Lefteris Pitarakis)