Russian intelligence services have been spying on the Sergei and Yulia Skripal for years and gained access to Yulia’s emails in 2013, according to a leaked letter from British intelligence services. The Guardian has obtained a letter written by Sir Mark Sedwill, British national security adviser, to Jens Stoltenberg, the secretary-general of NATO. The letter details why Britain concluded that the Russian government was behind the attempted murders of the Skripals using a Novichok nerve agent, claiming that they know Russia previously tested the deadly substance on door handles—the method believed to have been used in the attack in Salisbury last month. Sedwill added: “We have information indicating Russian intelligence service interest in the Skripals, dating back at least as far as 2013, when email accounts belonging to Yulia Skripal were targeted by GRU cyber specialists.” The GRU, known in English as Main Intelligence Directorate, is the foreign military intelligence agency of the Russian army. Yulia Skripal was discharged from hospital this week; while her father remains in the hospital, his condition is said to be improving.