Scotland Yard has formally accused Russia of carrying out a nuclear attack on the streets of London for the first time. Years of painstaking investigation and forensic workhave convinced British law enforcement agents and the security services that the Kremlin was behind a dastardly plot to assassinate a Russian defector with a cup of tea laced with the radioactive isotope Polonium-210. “Our silence must now end,” said the lawyer representing Scotland Yard, on the penultimate day of the inquiry into the death of Alexander Litvinenko. Litvinenko, a former KGB and FSB agent, died a slowly, and in great pain, in November 2006. Several weeks earlier he had taken tea with a former Russian intelligence operative at a luxury hotel less than a mile from Buckingham Palace. The radioactive substance that killed him was eventually detected in hair samples and traced, via a teapot at the Millennium hotel, all the way back to Moscow. “The… investigation has always had, at its central core, the s...