"Spent the day being an actor in the new Bridget Jones movie. Loved it, you're gonna love it too. Photo by @gregwilliamsphotography @workingtitlefilms #bridgetjones and #bridgetjonesbaby," he wrote in an Instagram post alongside a photo of him taking a selfie, with the movie's star Renee Zellweger peeking out from behind his shoulder.
He did not reveal who he will be playing in the followup to 2001's Bridget Jones's Diary and 2004's Bridget Jones: Edge of Reason.
The three movies co-star Colin Firth and are based on the writings of Helen Fielding.