Meet the Thirteenth Doctor (TV story)
From Tardis Wiki, the free Doctor Who reference
Meet the Thirteenth Doctor was a short teaser and announcement revealing the casting of Jodie Whittaker as the Thirteenth Doctor. It was broadcast on BBC One almost immediately after the conclusion of the Wimbeldon Men's Final. It followed the revelation that Peter Capaldi was stepping down from the role which was made public in January.
Prior to the announcement a promotional teaser was released on 14 July. The content of the teaser consisted of the number 13 being written in many different places around the world and stated that the announcement would be made that weekend.
