5. Kim Philby
Kim Philby stands out as one of the most damaging spies in British history. As a high-ranking member of MI6, he secretly worked for the Soviet Union as part of the infamous Cambridge Five. For decades, Philby fed critical intelligence to the USSR, compromising countless Western operations and exposing agents. His betrayal came as a shock to his colleagues and allies, shaking trust within the intelligence community and leaving a legacy of deep suspicion.
