longjackets:

There was something about Pearl that made all of us pay attention. She stood out above some really great candidates.

So we invited her in for a second audition, this time with Peter [Capaldi], to read with him, with fuller versions of those scenes – and it became even more apparent that Pearl, out of the five or six that we brought back in, was the one who played off Peter in the most interesting and exciting way.

You could see Peter’s excitement. He came to life. He was really responsive to Pearl. They had a chemistry. (x)