The peculiar evil of terrorism and insurgency is that not only do they cause great suffering, they also seek to deny a society choice in their political future. By using violent means to subvert democracy, insurgents have emerged throughout history under a variety of banners. States, bound to protect their citizens, have met insurgents in a battle for the support of the civilian population and to respond to the challenging of their legitimate monopoly over the use of violence. This study seeks to help states in their fight against terrorism by analysing three case studies in modern British history and determining what lessons may be learned. The British campaigns in Malaya (1948-60), Northern Ireland (1969-1998) and Afghanistan (2001-2021) are used to expose key themes in counterinsurgency. This study uses a comparative analysis method and considers a mix of qualitative and quantitative sources. A thorough analysis of the strategies and policies employed, their effectiveness, and the nature and tactics of insurgent movements, are explored. Resulting from this analysis are a set of five principles conducive to success in the British approach which may inform future models in counterinsurgency.