The Wire star also appears in the clip for the folk rockers' single Lover Of The Light video, which was shot in the Welsh countryside, and the band is thrilled with the result.
Britain's The Sun quotes the group as saying, "We are huge fans of Idris' work, as he's the most bada** British actor since Richard Briers. So we trusted him.
"We've been fortunate to work with some great directors but we've never really enjoyed being in videos. Talking to Idris and Dan (Cadan, scriptwriter) about making a video that we're not in made it a lot more fun.
"They wrote the treatment after our ale-infused conversation in a pub in London. What they directed we are proud to present."
In a post on his Twitter.com page, Elba links to the clip and adds, "I want to share this with you... I wrote & directed this video for Mumford And Sons. Very proud amazing song."