According to Doctor Who’s Costume Designer, Series 12 is in pre-production.

Ray Holman stated as such on his online CV.

Holman further added on Twitter yesterday that Jodie Whittaker will be back filming in 2019. He wrote:

All my lovely projects are clashing in 2019. Liar 2 is filming, The Split 2 is filming and so is Jodie’s second series of Who. I’ve been asked to design all three but I can only do one, they ALL clash. I love them all. What to do?

Although this is not an official BBC confirmation, this is the first mention of Series 12 from someone actually working on the show since the recent rumours of delays.