The BBC has a "board" for each interview, including the immediate supervisor to the role and a couple of other people who would potentially manage some aspects of that role or work in coordination with the successful candidate. It was all over Zoom because of COVID and I was given about a week's notice.
The questions were a mix of the usual (why do you want to work at the BBC) and competency-based (how would you deal with situations like this). Come armed with lots of story ideas and give examples of what you have done in the past that show your competency to do the job you are interviewing for.
It is a fairly intense process, and they ask a lot of very detailed questions and it's good to prepare in advance and practice your answers out loud. Many of the questions were also testing your familiarity with the BBC, which can be a bit hard for an outsider, so try to get as much insight into how the company works from anyone who has worked there (especially in the same team).
They went with an internal candidate for this role, which I understand is fairly common at the BBC, but they appeared really keen to make the process as fair as possible and I felt they made every effort to treat everyone equally. They were helpful before and after the interview, and it seemed like a good place to work, even if it is hard to get in as an outsider.
The HR is yet to get back to me about feedback from the interview, which is not very helpful. But the interviewers themselves have been so kind and generous with responding to emails that I am inclined to think this is a slow-moving bureaucratic issue with administration that is sometimes common with big organizations.
Read the tips for interviewing on the BBC website, it's very helpful. The interview experiences posted here helped me a lot as well.