Records of the Security Service and its predecessors are contained here.
World War I historical reports and other papers, 1908 to 1939, are in KV 1, personal files in KV 2, subject files, 1905 to 1919 in KV 3 and Second World War historical reports in KV 4. Organisation files are in KV 5 and List (L Series) files are in KV 6 .