Sienna Miller has revealed she could not wait to get back to work as she makes her big-screen return in Foxcatcher, which premiered at the BFI London Film Festival.

The 32-year-old, who plays wrestler's wife Nancy Schultz in Bennett Miller's true-life tale, outshone her co-stars Steve Carell and Vanessa Redgrave, shimmering in a metallic striped gown at the American Express gala in Leicester Square.

She said the role, the first of five films she has shot since becoming a mother to two-year-old daughter Marlowe, came at the right time.

Her forthcoming movies, all scheduled to be released in 2015, include the Clint Eastwood-directed American Sniper, Ben Wheatley's High-Rise and an as-yet-untitled John Wells project.

"I'm really looking forward to it all. I really wanted to work hard. I didn't work for a year after my daughter was born, and I really wanted to knuckle down this year and get a lot under my belt," she said.

"She started nursery about a month ago. I wanted to get to a point where I could be a bit more selective. So hopefully now that I've put in all this work this year, I'll be able to have a bit of an easier time the year after."

Sienna - who is engaged to Marlowe's father, actor Tom Sturridge - said the couple share parenting duties.

"We take turns. It's difficult but she's small enough that she can come with me everywhere so it's in a way, a great profession," she continued.

Foxcatcher, based on real-life events, tells the story of chemical fortune heir John du Pont and his friendship with Olympic medal-winning wrestling brothers, Dave and Mark Schultz - played by Mark Ruffalo and Channing Tatum - which ended in tragedy.

Carell, who plays du Pont, admitted he had to wrestle with his dark side to get into character.

"I don't think it was easy for any of us. It was a very complex world to look into. It wasn't easy, it wasn't simple and it took a long time to research it and think about it," he revealed.

Both the Despicable Me star - whose performance has been winning praise - and director Miller said they were in awe of British actress Vanessa Redgrave.

"It was intimidating. She's such a wonderful actress but she made me feel comfortable. So it was intimidating going in but just such a pleasure to work with," Carell, 52, said.

Miller added: "Vanessa was such a pro. We worked in a fairly unconventional way and she was just really good with it."

Foxcatcher opens in UK cinemas on January 9, 2015.