Hey, he said it, I didn't!
“I’m going to marry Patrick,” he said before pausing and realizing that could be taken out of context. “How else do you put that? I’m going to officiate at his wedding.”This revelation came during McKellen's appearance on The Jonathan Ross show. Congratulations to Sir Patrick!
Read more at the Wired story below, which includes video of the interview.
(*) Note the misspelling of McKellen's name in the URL! Don't you hate it when your content management system won't change the permalink when you edit the post title? I get that a lot.