There are at least two relevant scenarios – the RC changing over time, temporarily or permanently, and the RC sending someone else to give evidence – and I think neither is forbidden.
The guidance I mentioned above discusses situations in which a more junior doctor might give evidence at the tribunal. I imagine that at least some individual hospitals have similar policies for their hospital managers’ hearings.
This is almost right but (as it’s a different topic really) I’ve tried to answer it at Paper reviews and uncontested renewals - #4 by Jonathan