X

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X
You may be looking for Kotris or Professor X.

As spoken by Sarah Jane Smith, X was the twenty-fourth letter of the alphabet, following W and preceding Y. (TV: The Masque of Mandragora, Goodbye, Sarah Jane Smith)

X was the Roman numeral for the number 10. (TV: The Man from MI.5 [+]Loading...["The Man from MI.5 (TV story)"], The Church on Ruby Road [+]Loading...["The Church on Ruby Road (TV story)"])

X was the Space Service security designation for the Dalek Inquisitor General during the Second Dalek War. This earned the incumbent Inquisitor General the nickname of Dalek X, a name which the Inquisitor General himself soon adopted. (PROSE: Prisoner of the Daleks)