The Companion to British History By Charles Arnold-Baker

Wikipedia:

The Companion to British History is a single-volume encyclopaedic reference work written by Charles Arnold-Baker and edited by his son Henry von Blumenthal. It was published by Longcross Press in 1996, and described by The Spectator as “arguably one of the most remarkable books ever written”. The Second Edition was published by Routledge. The Daily Telegraph, in an account of how the book came to be written, described it as being “bigger than a foundation stone, longer than the Bible”.

Wikipedia: 

Charles Arnold-Baker, OBE (born Wolfgang Charles Werner von Blumenthal; 25 June 1918 – 6 June 2009) was an English member of MI6, barrister (called 1948) and historian. He was the author of the Companion to British History. He was awarded an OBE (1966) and the King Haakon VII Medal of Freedom (1945).

Charles Arnold-Baker was the son of Professor Baron Albrecht Werner von Blumenthal (10 August 1889, Staffelde, by Stettin, Prussia – 28 March 1945, Marburg an der Lahn), of Gross Schloenwitz by Stolp, Pomerania, by his first wife, an English lady, Wilhelmine, née Hainsworth (1883–1978), and stepson of Percival Richard Arnold-Baker.[1] His parents divorced in 1921; his mother returned to England and was remarried, in 1923, to Percy Arnold-Baker, (1875–1944), brother of Sir Frederick Arnold-Baker.) He was born in the Charité Hospital, Berlin, of which his ancestor Johann Christian Theden had been Surgeon-General, in 1918 and died in 2009, having been received into the Roman Catholic Church on his deathbed. His ashes were interred, however, in the triforium of the Temple Church, London.

. . .Charles then took part in the liberation of Norway, where he captured the complete Gestapo archive which enabled him to arrest fugitive Nazis, including Karl Fritzsch, the Deputy Commandant of Auschwitz. In his 2007 memoirs, For He Is an Englishman, Memoirs of a Prussian Nobleman, Captain Arnold-Baker recorded that as an MI6 officer in Oslo he arrested Fritzsch: “We picked up, for example, the deputy commandant of Auschwitz, a little runt of a man called Fritzsch whom we naturally put in the custody of a Jewish guard – with strict instructions not to damage him, of course.”

He also arrested senior German military figures[dubious – discuss] (King Haakon VII’s Medal of Freedom). He took the view that as the war was now practically over, it was important to gather as much intelligence about the Soviet army, since this was plainly the new threat. In this he was thwarted, and his reports concerning his interrogations of such figures as a high civilian official in the German administration of occupied Russia, von der Ow, who described the anti-communist feelings of much of the population of the western USSR, were buried by his superiors who were, as it later emerged, Soviet spies. It seems that as a consequence he voiced suspicions about Philby which were later conveyed by M. Oldfield to Washington.