In the breaks between scenes, Catherine, David Tennant and various space-suited actors sit around a small table in the green room, playing card game Switch, while Alex Kingston tackles the Daily Telegraph crossword. (“A large barrel? Three letters?” she wonders out loud. “KEG!” replies everyone within earshot.) Meanwhile, Catherine plays her Ace of Hearts, prompting David to exclaim, “Now, why would you want to do that?”
“Because I’m going to win,” she whoops. “Get in! One card left!”
“Is that so?” David laughs. “Just sit still, missy. Sit still.”
Afterwards, David sets the record straight: “Catherine gets too competitive,” he smiles, cheekily. “It blinds her - blinds her to the tactics. She gets overexcited. She needs to breathe. She wasn’t winning! She was fighting a losing battle.”
“Was David claiming that he was the best?” chips in Catherine, surveying her co-star with an impish eye. “Well, he wasn’t the best. He’s deluded. I was the head of the leaderboard by a mile.” The score sheet on the wall indicates that she’s beating David 13 games to 10.
“Can we step you back on set, please?” requests Dan mumford, the First Assistant director.
Catherine gasps. “But I’m about to win!
— excerpt from an interview with Catherine in the Doctor Who magazine (via stellapiumata