Were other people from the Crown at the Bafta dinner? And doesn’t him being there without walking the red carpet (even though he’s hot stuff right now with The Crown) could be taken as a sign that he was there with her and not for The Crown?

I don’t know if there were other people from The Crown, but it was the BAFTA cinema. PM is also a movie writer, he has several projects in development, so him being here, for The Crown or not, is no surprise. If he was there to support her, he would have posed with her and sit with her.