A friend of mine volunteers to work with Alzhiemers patients in a hospital and one of them can remember very little except for song lyrics. He keeps asking her if she can get the lyrics of a song to which he knows just one verse. Can anybody help please. The verse he knows is:

I'm only an Irish laddie
I'm part of the rank and file
Though I fight for the British army
I'm a son of Erin's isle