That is the point. There are so many parties with motive including the British Crown. The UK secret service have form in this sort of thing. The most spectacular is the strangulation of the president of American Standard Oil by a Canadian from Winnipeg in the UK secret service. The president of Standard oil AMOCO was strongly pro German and assisting the Germans. Churchill had his assassination ordered on American soil long before the US entered the war. This crime was unsolved until it was declassified and owned up to in the agents autobiography: "A Man Called Intrepid". The latter was his code name.