Purpose of the study: To explore in detail the terror of the period of the first Russian revolution in the assessment of British diplomats during the revolution of 1905-1907.   Methodology: The research is based on archival documents, most of which are introduced into scientific discourse for the first time, as well as periodical press materials of that time. The research draws from the documents of the British National Archive and the Russian State Historical Archive (fund: 1276 - Office of the Council of Ministers). The article employs chronological, historical-typological, historical-genetic, comparative and illustrative research methods, as well as systematic analysis and synthesis.   Main Findings: The research suggests that in 1905-1907 terror affected not only Russian but also British citizens. British reaction to terror in Russia slowed down the signing of a foreign policy agreement between the countries.   Applications of this study: The study may be used by historians and everyone interested in the questions of the First Russian Revolution as well as the history of diplomatic relations with Britain. The results of the study can be used in universities to study the history of Russia and the history of international relations at the beginning of the 20th century.   Novelty/Originality of this study: Many historians focus on terror in Russia during the revolution of 1905-1907. However, the reflections on revolutionary terror by British diplomats did not become a subject of research in Russian or foreign historiography.