Reese in "Four Christmases"

"What Hollywood power?" she laughs today in Beverly Hills, poised and unassuming as always in support of her new comedy Four Christmases. "What are you talking about?" It's a rhetorical question, of course. Witherspoon knows as well as anyone the value of her business portfolio. "People talk about Hollywood power or say you're on a list and that feels wonderful. Obviously it really creates opportunities I didn't have before."

But Witherspoon is packing a different kind of power now, a personal one emanating from a difficult time in her life which saw her separating from husband Ryan Phillippe in 2006. Now divorced, she has two children with Phillippe (Ava, nine, and Deacon, five) and a boyfriend who's a power player himself (Jake Gyllenhaal, with whom she starred in last year's Rendition).

"I'd never seen anyone do the idea of the blended family and how they have to go to a million different places at Christmas. But I hear people complain about it constantly and it's a situation my own children will have to deal with."

Four Christmases is a perfect example of Witherspoon wielding her power too for personal gain, in making a film for her children – albeit one they won't be able to appreciate or fully digest for a few years. "No," she mock-admonishes, "This is not for your children. It's a PG-13 [admission for children under 13 strongly cautioned]. But my family always went to movies on Christmas Day – The Godfather, The Elephant Man. Your typical cheerful holiday fare. It's fun to go to the movies at Christmas and nice to be part of a movie that at least grown-ups and teenagers can see. Plus it means a lot when I get to have experiences where I meet young people and they say, 'You know, this is the movie that got me through a hard time' or, 'This is the movie I watch with my family'."The Vaughn-Witherspoon pairing appears on paper to be a must-succeed no-brainer. He, like her, is a proven dramatic actor with a natural inclination for comedy, though there were practical considerations like the filming-unfriendly height gap (he's 6ft 5in and had to carry her in some dancing scenes so their heads would fit in to the same frame). It has been reported that the pair did not get on – Vaughn is more conservative than Witherspoon politically – though she laughs off such reports, consummate pro that she is.
Of course she is here for the purposes of film promotion but even out and about these days, on the arm of Gyllenhaal, she has been beaming broadly for paparazzi photographers. It is quite a change for a woman, who only a year ago was furiously denying what most of Hollywood knew to be true; that she and Gyllenhaal were indeed an item.Witherspoon's circumspect stage-managing of her life was certainly to protect her children but she has now apparently become more open. "Oh, it's not that formal," she says, relaxed and non-defensive on the question of how she and Phillippe will handle custody over Christmas. "There's a lot of communication and just being very open about things. It's nothing contentious, all very go with the flow."
I ask how would she describe her own personal power these days – emotional and spiritual rather than career-oriented. She is initially stuck for words. Finally, she sits bolt upright with her verdict. "I'm not wishy-washy. I'm just very clear. I tell people what I feel about things. If I'm mad at you, you know within a minute. There's no ambiguity. It's nice to be in this place. I'm getting older and I'm not as fearful of other people's ideas of who I am. I'm becoming clearer about that myself and am able to express myself better."
She lives with the children and, quite often, Gyllenhaal on that farm not far north of Los Angeles. There has been talk of marriage at Christmas but Witherspoon insists otherwise. "I don't think about it much." There will certainly be church on Christmas Eve. "I love to hear the music and be quiet and thoughtful about what the holiday really means for me." Which is? "Cooking, playing games and kids. It's all about them."

What about New Year's Resolutions? "Not yet. Gosh. I just try not to look too far into the future. It gets terrifying and daunting if you look at the big picture. Can't we just get through Thanksgiving?"

'Four Christmases' opens on 26 November