Rupert of the Rhine

Rupert 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
Unremarked in Mark Gatiss' account was the fact that "Rupert" was Prince Rupert of the Rhine — perhaps because that's such an obvious fact of English history. However, Gatiss does have Sir Harry Cooke call him "Majesty", leaving little doubt, if any were actually present, of Rupert's highborn status.