Postcard (A Lady Doctor?)

After her regeneration, the Thirteenth Doctor sent Iris Wildthyme a postcard, which informed Iris of the Doctor's recent change.

The front of the card depicted the Doctor standing in a forest, holding the TARDIS key. (PROSE: A Lady Doctor?)

A later source clarified that this postcard had not actually been sent by the Thirteenth Doctor, but her "actualised potential". (PROSE: )