London Guardian 
June 17, 2013
American spies based in the UK intercepted the top-secret communications of the then Russian president, Dmitry Medvedev, during his visit to Britain for the G20 summit in London, leaked documents reveal.
The details of the intercept were set out in a briefing prepared by the National Security Agency (NSA), America’s biggest surveillance and eavesdropping organisation, and shared with high-ranking officials from Britain, Australia, Canada and New Zealand.
The document, leaked by the NSA whistleblower Edward Snowden and seen by the Guardian, shows the agency believed it might have discovered “a change in the way Russian leadership signals have been normally transmitted”.