My father is known by his middle name, and always has been but his parents thought that it might be a difficult name for school, so they gave him a much more "normal" first name just in case. We were going to do the same when we were expecting ds2 (but turned out to be dd instead, so never had the opportunity). I don't think it has ever caused my father any problems, he always uses both names on anything official, which is what we would have done too. It's not particularly unusual - I have quite a few friends that decided to use their middle names at university (although it was confusing if their parents didn't go along with it!). I think that for Gordon Brown it's probably a family tradition as their second son is Jame Fraser, but known as Fraser. So he's probably never been called James (so nothing to do with "get up, get on donw")