Rupert of the Rhine

Prince Rupert of the Rhine was the leader of an 18,000-man strong army that fought against Oliver Cromwell at Marston Moor in the English Civil War. He was soundly defeated. (PROSE: Nightshade)

Behind the scenes
While Mark Gatiss did not use the title "of the Rhine" explicitly, he stated that Charles I was Prince Rupert's uncle, thereby identifying him beyond any doubt.