Sisi

Empress Sisi, as Empress Elisabeth of Austria was commonly known, was the wife of Emperor Franz Joseph of Austria when the Eighth Doctor visited Vienna with Mary Shelley in September 1873.

She was friends with Countess Mitzi Wittenmeier. Alfred Stahlbaum, obsessed with the Empress, was hoping that she might take interest in the performances of the Silver Turk, who was in fact a Cyberman named Bremm. He asked Mitzi to drop in a good word for him with her royal friend.

In the end, Sisi sent a letter with Ernst Bratfisch, in which she invited Stahlbaum to attend the Hofburg Palace with the Silver Turk. But the performance did not happen because another Cyberman, Gramm, intercepted Stahlbaum on the way to the palace and took Bremm with him.

Knowing about Stahlbaum's obsession with the Empress, Johan Drossel later employed a puppet of the Empress to try to persuade Stahlbaum to join forces with him again. (AUDIO: The Silver Turk)