The papers spent years hidden in a milk churn beneath a Russian dacha and read like an encyclopedia of Cold War espionage. This undated image made available by the Churchill Archive Centre shows the Mitrokhin Archive stacked on a shelf at the Churchill Archive Centre in Cambridge England. Original documents from one of the biggest intelligence leaks in history - a who's who of Soviet spying - were released Monday July 7, 2014, after being held in secret for two decades.