Not a very good headline, but I love the glimpse behind the scenes.
I watched this video the other day expecting pretty fluffy content, but I was similarly impressed by the discussion of just how much it was Millie Gibson's show during the first filming block.
I'm not sure I can think of another modern companion that would have carried that episode that well, especially as their first week of work. Donna's the most complete companion for me, but she's a very different vibe. Billie Piper's also really good when she's given the chance but I don't know that Doctor Who ever gave her that much chance. Clara by the end but it took a few series I think.