31/01/2012 03:17 GMT | Updated 31/01/2012 07:43 GMT

Reese Witherspoon Braves The Cold For 'This Means War' UK Premiere (PHOTOS, VIDEO)

Reese Witherspoon brought some heat to a freezing red carpet, promoting a film which lets fans see her sexy side.

The 35-year-old, who won an Oscar for playing June Carter Cash in Walk The Line, plays a spy at the centre of a love triangle in This Means War.

The starlet braved the British winter in a green and black sequinned Louis Vuitton minidress, and said she enjoyed vamping it up for the role.

She said: "I think everybody grows up, you become more mature and you want to explore different kinds of stuff, but it's a very fun comedy too."

Director McG (Joseph McGinty Nichol) said: "She's very sexy in this role. I said to her, 'Men really like you and you're America's sweetheart, the world's sweetheart', but we went further with some overt sexuality, gave her a little bit more volume in her hair, a little smokiness to her eyes.

"A bit more va-va-voom in a knock-out kind of way and she went for it, and she's really up there on the kitchen counter making out with Chris Pine, then doing the same thing with Tom Hardy."

Witherspoon, who married agent Jim Toth last year, said having co-stars Hardy and Pine fight over her was "great".

"I'm not going to lie. It wasn't a hard day to go to work," she said.

This Means War is out in cinemas on March 2.

SLIDESHOW: The This Means War stars on the red carpet...

This Means War Premiere