The actress, who was first seen with the music-man at a small Mumford & Sons gig in Nashville in February, reportedly got engaged over a weekend getaway at Babington House in Somerset. An anonymous source told The Sun that Carey was wearing a beautiful ring and didnt seem to mind who saw it.
The close-knit couple has enjoyed a whirlwind romance that has taken them from London, to the Orkney Islands, to Mumford & Sons concert dates across the US.
Mulligan, 26, and Mumford, 24, are no strangers to high-profile romances. She dated Shia LeBoeuf, and Mumford had a long-term relationship with folk singer Laura Marling before meeting Mulligan.
Congratulations to the happy couple. Now: what will she wear? Considering her propensity for high-necked, full-skirted dresses from the likes of Roksanda Ilincic, Peter Pilotto and Prada, we're thinking a vintage-inspired dress with a ballet-length skirt could do the trick. Take a look at her Style File for sartorial hints...