Richard J. Popplewell & Richard James Popplewell 
Intelligence and Imperial Defence [PDF ebook] 
British Intelligence and the Defence of the Indian Empire 1904-1924

This is the first book to appear on British intelligence operations based in both India and London, which defended the Indian Empire against subversion during the first two decades of the twentieth century. It is concerned with the threat to the British Raj posed by the Indian revolutionary movement, the resulting development of the imperial intelligence service and the role it played during the First World War.