Both Donna and Rose challenged him and respected him but didn't let him get too full of himself. Rose taught him how go on. But Donna taught him when to stop. He needed both of them. Catherine Tate was a magnificent foil, a magnificent companion. The stories are so strong because of her... Pompeii, the planet of the Ood. Donna drives the stories. Then I watch her and Handy in the TARDIS being absolutely brilliant, and deny the rest.