Ronson, 35, produced pal Amy Winehouse's classic album Back to Black -- and his late friend's absence was keenly felt at the bash, an insider says.
"Amy was a great friend of both Mark and Josephine and they would have been thrilled to have her with them at their big day, but sadly it wasn't to be," says the source. "Amy would definitely have sung one of her hits at the wedding if she were still alive, as she meant to much to both of them. Her death devastated the pair of them."
Still, the day, organized hastily by the pair since their Feb. 2011 engagement, went by swimmingly. Guests included his sister, DJ Samantha Ronson, her fashion designer twin Charlotte Ronson, model Kate Moss, singer Lily Allen, his socialite-writer mom Ann Dexter-Jones and stepfather, Foreigner's Mick Jones.