Representatives for the couple confirmed that they tied the knot three years ago in New York, reported Ace Showbiz.
The news was revealed in an interview with Germany's Bild newspaper when Rickman, 69, was asked what was the secret to successful relationship without getting married.
"We are married, just recently," the actor surprisingly answered. "It was great because no one was there. After the wedding in New York, we walked across the Brooklyn Bridge and ate lunch."
According to the newspaper, in lieu of a big diamond wedding ring, Rickman gifted his 68-year-old new wife with a simple USD 200 band that according to him, "she never wears."
Horton is an active member of the Labour Party. She has served as a councilor in the London Borough of Kensington and Chelsea and worked as an economics lecturer at Kingston-upon-Thames University.