The most obvious one is from the Blag magazine article where he is facing profile and making a boxer pose. You can see from the top of his head that his hair appears to be thinning a bit. Of course, I could be wrong. Also, just look at the more recent photos of him and you may notice that the hair on the crown of his head near his forehead is where it looks (to me, anyhow) where his hair seems to be thinning and receding.