On 16 July 2017, the BBC announced that Whittaker would become the thirteenth incarnation of The Doctor in the British TV series "Doctor Who". She formally assumed the role from Peter Capaldi in the 2017 Christmas special episode "Twice Upon a Time" when Capaldi's Twelfth Doctor regenerated into Whittaker's Thirteenth Doctor. Whittaker appeared in her first full series as The Doctor in the eleventh series, which premiered in October 2018. She continued in the role in the twelfth series in 2020. Whittaker later announced that she would reprise her role as The Doctor into its thirteenth series.