Cult
Rex Features
The actress, who left the cult show in 2006, has banned Fox from watching the series in case he sees an episode with her in it.
"He has never seen an episode of Doctor Who with me in it because I won't let him," she said.
Billie added that she found it impossible to watch herself on screen, saying she's afraid others would make fun of her performance.
"I get really edgy watching myself, and I get even more edgy with my loved ones because they know me and I feel they're going to take the mickey," she said.
"Sitting down to watch my performances makes me cry. It's even worse watching it with another actor, because he can dissect your performance."
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