 Tomlinson worked in the "SOV / OPS" department, operating during the ending phases of the Cold War against the Soviet Union. He was posted to a diplomatic role in Moscow, and was one of the agents responsible for the retrieval of the valuable Mitrokhin Archive in 1992. From March 1992 until September 1993 he worked in the Eastern European Controllerate. Whilst working there, it was discovered that the Conservative Party had been receiving donations from Serbian supporters. In November 1993 he joined the Balkans Controllerate, and was posted to Sarajevo for six months as the MI6 representative in Bosnia during the breakup of the former Yugoslavia. There he was a "targeting officer", with a mission to identify potential informants and gather intelligence. A soldier who escorted Tomlinson to Bosnia described him as a "liability", a "sulk" and "totally unprofessional", although Tomlinson has disputed this.
