Eventually Helen Mirren will run out of European monarchs to portray onscreen, but not today. Mirren has signed on to star as Russia’s Catherine the Great in a four-part mini-series produced by HBO and Europe’s Sky network. The series “will follow Catherine toward the end of her reign and her passionate affair with Grigory Potemkin,” according to a report in The Hollywood Reporter. “Unable to publicly marry and famously promiscuous, they develop a unique and devoted relationship, overcoming their adversaries and together shaping Russia as we know it today.” Nigel Williams, who wrote the script back when Mirren played Elizabeth I on TV, is writing Catherine the Great, with Prime Suspect’s Philip Martin directing. If she doesn’t win an Emmy for this, maybe Mirren will simply end up in charge of a European principality herself.