I believe that the song had its origins on Arrse (where else...?) for a spot of banter at the Army vs Navy match.
The thread you want is
here.
For those of a touchy feely disposition, I should point out that the link leads to an MS Word Doc which contains two songs, and the naughty army chaps make a disparagingly stereotypical observation about the sort of headgear favoured in Iran and the Middle East in the second one. So don't say you weren't warned, OK?