In May 1940, 20-year-old Len Thorne joined the RAF, as did many young men during the Second World War. After two hectic tours of operational duty as a fighter pilot, including some desperately dangerous low-level flying at Dunkirk, he was posted to AFDU (Air Fighting Development Unit) and remained there as a test pilot for the rest of the war. Fortunately for us, Len kept a detailed diary, which, set alongside his log book, tells the unique story of a test pilot tasked with developing operational tactics and testing captured enemy aircraft, such as the feared Fw 190. During Len's career, he worked alongside some of the most famous fighter aces and his records cast light on some of the most famous flyers of the RAF, including Wing Commander Al Deere and Spitfire aces Squadron Leader ‘Paddy’ Finucane, Ernie Ryder and many others. A unique record of military aviation history, From Spitfire to Focke Wulf offers a window to this era of rapid and high-stakes aircraft development.