Carey is said to have become friends with the actor when they were both nominated for a host of movie awards, including the Oscars, in 2010 - Mulligan for An Education and Firth for A Single Man.
A source told The Sun: "She thought it would be funny to have the actor address the room. Unlike his character in The King's Speech, Colin was a pro at the speech. He was his charming self and had the room in fits."
Reports claim Marcus and Carey were married in a converted barn by the groom's father, who is a vicar.