Tom Ford and Hamm

Ford, however, bristles at the Mad Men comparison. “It’s pure coincidence—even though I do use Jon Hamm from Mad Men in a voice-over role. There is nothing about Mad Men and A Single Man that are similar except that they are both set in 1962.”
http://www.advocate.com/arts-entertainment/film/2009/11/09/visionary-tom-ford

Cameo: [Jon Hamm] Mad Men’s Jon Hamm is the uncredited voice of Hank Ackerley, the man who calls Colin Firth’s character at the start of the film.

For the big phone call scene, did you put John Hamm on the phone as a 1962 in-joke?

Tom Ford: No, it’s so funny because I’m not allowed to mention the person on the other end of the phone’s name because I was sitting next to this person at a dinner party and I know him. I said I’m looping something tomorrow and your voice is perfect, would you come in and do it? And then his agent ripped me apart like you can’t imagine. So, all I can tell is I don’t know who’s voice that was in the film.

http://www.newnownext.com/tom-ford-interview-a-single-man-opens-in-nyc-ford-talks-gayness-movies-fashion-jon-hamm/12/2009/