SPOILERS (sweetie), for the coming season of Doctor Who, do not proceed beyond the picture.
So the new companion, Bill Potts played by Pearl Mackie is going to be the first openly gay Doctor Who companion. Now, this comes with some caveats that I am not really interested in rehashing but it is a major step. This is the series' co-lead we're talking about and we're told her sexuality will be an open, confirmed thing.
This isn't going to be a bunch of jokes about Jane Austen (Clara), a character who will disappear after five episodes (Jack), a recurring guest star (River), a set of tropes in a school uniform (Turlough) or an expanded universe character comparatively few fans will ever hear of (Oliver Harper, Chris Cwej, Fitz Kreiner). This is an out and proud, one hundred percent definitely gay character holding down the second most prominent role in the show.
Also, she's a gay woman of colour, which is a combination that doesn't happen often enough in fiction because of a strange psychology that makes people think “That's too many extra things!” deviating from the straight white male template that is, of course, the pure and unaltered human being.
What's more, given Moffat's track record on these things she's unlikely to end up dead at the end of the season. Okay, all of Moffat's companions have confirmed deaths but Amy, Rory and Clara all had long, full lives before the end. They didn't just drop dead when the Doctor was done with them, is what I'm saying.
(Okay, no, I don't think she's going to be in more than one season. I think Chibnall, like Moffat, will want to start with his own Doctor and his own companion to tell his own story and I can't hold that against him. I could be wrong, but the BBC certainly seemed to like the clean break of Series Five/One/Fnarg and I reckon they'll want the same for Series Ten.)
I look forward with immense anticipation to Bill meeting Missy. I really want to see the Master doing her “seduce the companion away from the Doctor” routine with a companion who might actually view is as seduction.