Black Dalek Leader

After the failure of the 22nd century Dalek invasion of Earth, the Daleks identified the Doctor and a Black Dalek, under orders from the Dalek Prime, (PROSE: The Chase) ordered an assassination squad to pursue his TARDIS in a Dalek time machine. The squad failed. (TV: The Chase)

The same Black Dalek, acting as a Supreme Dalek, oversaw the Dalek operations on planet Kembel in the year 4000. It was wiped out when the Doctor hijacked the Time Destructor. (TV: Mission to the Unknown/The Dalek's Master Plan) This was a massive blow for the Dalek Empire as the Dalek Prime considered both the fleet and the Black Dalek irreplaceable. (PROSE: The Mutation of Time)

Behind the scenes

 * John Peel's novelisations establish the Black Dalek from The Chase and The Daleks' Master Plan as one and the same. Reference to this Dalek being "irreplaceable" in The Mutation of Time also heavily implies it to be the same individual as the Black Dalek Leader featured prominently throughout The Dalek Chronicles. This latter link has yet to be formally established, however.
 * The Supreme Dalek was voiced by either David Graham or Peter Hawkins in its original televised appearances. Nicholas Briggs provided its voice for the novelisation audiobooks, as well as the reconstruction of Mission to the Unknown by the University of Central Lancashire.