EXCUSE ME BUT THIS RING. NO ONE NOTICED IT?????
Actually I’ve seen people mention it since the first episode.
It’s Capaldi’s wedding ring. He never takes it off, even when acting.
To add to the story, he refuses to take it off because when his acting career was struggling, his wife never gave up on him. When he landed his first major gig, he decided to not take it off, to represent he was there because of his wife’s support.
I read somewhere that if you look closely it’s two rings, one is his wedding ring and over that a ring he had made similar to Hartnell’s ring. The story behind that ring is that “he stone represented, and reminded the Doctor of, all the people he’s lost in his long life. But it wasn’t a sad thing. It was to remember how joyful times could be. If you travel in time and space, most of the people you know and love will eventually be gone. But you’ll also be able to go and find them again.”