At first glance, I feel there is something a little "off" about this signature. You mentioned you got this auto TTM. I can't speak from experience as I haven't written to him personally, but I have heard from other collectors that David Beckham doesn't sign authentically TTM (IP is another story). While it is possible that David could have signed a stack of photos in advance to be sent out to collectors, I feel it is more likely that what you have is a secretarial signature.