David Tennant praises newcomer Freema Agyeman in an interview today on Sci Fi Wire.
In the interview, conducted by e-mail, he tells the Sci Fi Channel's news service that the actress "hit the ground running" when she took on the role of Martha Jones, and said he let her deal with the pressure of replacing such a popular and high-profile cast member as Billie Piper in her own way.
Tennant says Agyeman "inhabited Martha Jones from day one without a hint of trepidation or nervousness. I found myself quite envious of her confidence. She is going to be brilliant."
He also tells of how difficult it was to shoot the final scenes with Piper, saying they started sniffling during a run-through of the lines on the make-up bus.
Tennant says Martha and the Doctor have an entirely different relationship to Rose and the Doctor, adding: "As with any big relationship, it takes time for the scars to heal. Perhaps the Doctor feels like he's dealt with it, but Martha might disagree." He also says she "makes herself indispensable".