When published in 2020 it offered the first comprehensive account of how intelligence influenced and sustained British naval power from the mid nineteenth century through to the end of the Cold War.  The book describes why and how intelligence was collected and assesses its real impact on policy and operations. It confirms that naval intelligence was critical to Britain's survival and ultimate victory in the two World Wars but significantly reappraises its role, highlighting the importance of communications intelligence to an effective blockade in the First, and according Ultra less dominance compared to other sources in the Second. It reveals that coverage of Germany before 1914 and of the three Axis powers in the interwar period was more comprehensive and effective than previously suggested; and while British power declined rapidly after 1945, the book shows how intelligence helped the Royal Navy to remain a significant global force for the rest of the twentieth century, and in