Hey, we could even see a reunion between the 14th Doctor and whoever this is with Rose’s face! How long Billie would stick around if this is the case would wildly fluctuate but

Piper, now 42, originally played companion Rose Tyler in 2005 alongside Christopher Eccleston’s Ninth Doctor. She went on to appear opposite David Tennant and was later revealed to be the mythical "Bad Wolf" - a mysterious, universe-shaping figure. Now, she’s taken the role full circle by stepping into the shoes of the Doctor herself.

"Billie once changed the whole of television, back in 2005, and now she’s done it again!," added showrunner Russell T Davies. "It’s an honour and a hoot to welcome her back to the TARDIS, but quite how and why and who is a story yet to be told. After 62 years, the Doctor’s adventures are only just beginning."