The Oster Conspiracy hoped to reinstate the grandson of which British Monarch as Emperor? 
Oster Conspiracy:  They planned to overthrow Hitler and the Nazi regime through a planned storming of the Reich Chancellery by forces loyal to the plot to take control of the government, who would either arrest or assassinate Hitler, and restore the exiled Wilhelm II as Emperor. Wilhelm II, German Emperor:  He was the eldest grandchild of the British Queen Victoria and related to many monarchs and princes of Europe.
British Queen Victoria