Sir Francis Harry Hinsley OBE (26 November 1918 – 16 February 1998) was an English historian and cryptanalyst. He worked at Bletchley Park during the Second World War and wrote widely on the history of international relations and British Intelligence during the Second World War. He was known as Harry Hinsley.
Hinsley was the son of a coal merchant. His mother Emma Hinsley (née Adey) was a school caretaker, and they lived in Birchills, in the parish of St Andrew's, Walsall. Harry was educated at Queen Mary's Grammar School, Walsall, and in 1937 won a scholarship to study history at St. John's College, Cambridge. In October 1939, while still studying at St. John's, he was summoned to an interview with Alastair Denniston, head of the Government Code and Cypher School (GC&CS), and was thereby recruited to Bletchley Park's naval section in Hut 4.
At Bletchley Park, Hinsley studied the external characteristics of intercepted German messages, a process sometimes termed "traffic analysis": from call signs, frequencies, times of interception and so forth, he was able to deduce a great deal of information about the structure of Nazi Germany's Kriegsmarine's communication networks, and even about the structure of the German navy itself.
Hinsley helped initiate a programme of seizing Enigma machines and keys from German weather ships, such as the Lauenburg, thereby facilitating Bletchley Park's resumption of interrupted breaking of German Naval Enigma.