Freema Agyeman.com the forums

http://blogs.thestage.co.uk/tvtoday/2008/04/doctor-who-44-the-sontaran-stratagem/
Freema Agyeman’s turn as Martha is played as effortlessly as always, and it’s nice to see the actress make the opening credits again. However, much like her triple turn in Torchwood, it seems her purpose here is to once again be tied up by the baddies and need rescuing. It’s a traditional role for the companion, and one that Martha seems to serve more than others. That being said, the chance for Agyeman to play evil clone Martha is one that the actress clearly relishes, so at least she’s not absent from the action as she was in her Torchwood episodes.

She certainly does relish it: "good is good but bad is wicked!" she said on the audio commentary.

who does'nt like being bad

Thanks for finding/sharing that 'GALLIFREYGIRL'

And I love the concept of an evil Martha....more challenging stuff for the wonderful Freema to have a go at.