Prince Felix Yusupov was a Russian aristocrat during the early 20th century. He resided in the Moika Palace in St Petersburg. Along with his co-conspirators Grand Duke Dmitri Pavlovich and Vladimir Purishkevich, he was responsible for the murder of the Russian mystic Grigori Rasputin in December 1916.
On meeting Rasputin in St Petersburg shortly before his death, the Third Doctor, Jo Grant and Liz Shaw realised that the legends about him were just that. He was not the evil manipulator that the history books had made him out to be. Liz reluctantly passed on Yusupov's invitation to dinner to Rasputin, knowing that he would be killed, but also realising that history must run its proper course. Jo posed as a maid in the kitchens at Yusupov's Moika Palace, where she disposed of poisoned cakes and wine intended for Rasputin and replaced them with untainted ones, unknowingly contributing to one of the last and most notorious chapters of his legend. When Rasputin devoured the cakes and remained unharmed, Yusupov became convinced Rasputin was possessed by the Devil and shot him in the back as he knelt in prayer. Purishkevich finished the job, shooting Rasputin repeatedly until he died and then beating his corpse in a fit of rage. (PROSE: The Wages of Sin)