Who is Popov from The Case of Comrade Tulayev and what is their importance?

Popov is a member of the Central Control Commission. Popov is unknown to the public, but he holds much power within the Party. He has thick, dirty-gray hair and an aging, deeply-lined face that is pimply from bad health. His nails are dirty and cracked and his skin is flabby. Popov also has a thin, faded beard and wears steel-rimmed spectacles. He hides under a guileless manner, but he is an old fox. Popov is eventually arrested principally because of his daughter's attempts try to save Rublev from execution.