How the rise of Militant Tendency transformed MI5’s perception of Trotskyism’s ability to pose a threat to the British state

Drawing on newly released files available at The UK National Archives, George Kassimeris and Oliver Price assesses how, between the late 1970s and early 1980s, Militant became the first and only Trotskyist group to be considered by MI5 a significant subversive threat to British internal security.