"I spent a lot of time in Utah running around the desert," says Karen Gillan. "It simply wouldn't have looked the same if we'd filmed it in Cardiff against a green screen. The desert backdrop really gives the opening two episodes an epic feel."
You'd think filming in the desert would be hot work but, at night, temperatures fell below freezing: "We were all 'thermalled' up and I had on two pairs of trousers and four tops! Then the sun would come up, making it blistering hot and we'd all peel off the layers," laughs Gillan.
Trousers? Yup, for some fans of Amy Pond that's the bad news. In the opening episodes of the new series, Amy will forsake her traditional micro-mini in favour of sensible trews and her high heels for trainers.
"It's true!" giggles Gillan. "I quite like the idea that she's getting a little bit more tomboyish as she becomes more of an action girl."
Then, of course, she's married. Not that this will change her, she insists. "I hate it when people settle down into a rut when they marry and get all subdued and a bit more boring. I was determined that that would never happen to her."
The new series marks a new start for the character Gillan simply calls "Pond". "As the Doctor rebooted the universe at the end of the last series, Pond's been given the life that she should have had," she reasons. "The life where she wasn't sat down by psychiatrists telling her she's crazy. She was obviously a broken person. She's generally a bit more settled now."
Pond may be more settled, but Karen Gillan can still be thrown by the twists and turns of the story: "Everything's so important and precise in Steven Moffat's scripts. There are a couple of throwaway lines in the opening two-parter, which I thought were just a couple of funny gags but turn out to be one of the most important things that Amy's ever said. And I didn't know that at the time!"
But where else would she get the chance to swash her buckle playing an intergalactic pirate as she does in "a full-on fight with no stunt double" in episode three of this series? "I'm wearing a miniskirt in that one," she reassures, "with some ridiculous pink tights, so I'm like a pink-tighted pirate! I love that so much."
A final thought. Who wears the metaphorical trousers on set? Has Matt Smith ever requested a cup of tea from the Doctor's "assistant"?
"Actually, he did try that the other day," she laughs dismissively. "He didn't get one." Enough said.