Tennant guest stars in Litvinenko played by Tennant

Litvinenko Episode 2 marked the first appearances in the series by Rad Kaim and Aleksandar Mikic.
Given David Tennant played the titular Alexander Litvinenko, Kaim and Mikic had been in Doctor Who episodes with Tennant as the Tenth Doctor as Kaim was in The Sontaran Stratagem playing Worker and Mikic was in The Waters of Mars playing Yuri Kerenski.

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