"Griffin" was the code name for a man the author believes was the British Secret Service's most important spy in World War II. Paul Rosbaud was the editor of Nazi Germany's leading scientific periodical and probably more fully informed about overall war-related scientific developments there than anyone. Kramish, a scientist who has served on the U.S. Atomic Energy Commission, maintains that Rosbaud, through his spymaster Eric Welsh, passed valuable information on jet aircraft, radar, V-1 and V-2 rockets, and the efforts of German scientists to develop the first atomic bomb.
Another interesting tale of one of WW II's 'secrets' that may never be resolved. Why? Because the Allies did or did not do things their governments would rather keep quiet, even to this day. To list them would take to much space.
But just as an example, did the British 'deliver', through a double agent, hundreds of French Resistance agents to help the credibility of that double agent, who was assigned to convince the Nazis that the invasion of Europe was to take place in the Pas de Calais area. If not, then why, when that agent was on trial for treason by a French court, was that agent released after a British official testified to the court in secret.
While the above is not mentioned in this book, the Allied effort to convince the Germans that 'heavy water" was essential to make an atomic bomb was mentioned. This was a deception that cost the lives of many people. A quicker route to development of the atom bomb was to use graphite, as the Americans were doing. And the Allies didn't want the Germans to figure this out. So the risking and loss of lives to destroy "heavy water" in German hands was essential to send the Nazi scientists down the wrong path.
We will never know all the secrets of any war, past or present.