I play the pipe march version of "Campbell's Farewell to Redcastle", pretty much as the Scots Guards book has it - it's a very common session tune in Scotland. The Cabar Feidh pipe collection (Queen's Own Highlanders) has The Galloway Hills as a slow march, almost the same as the usual version of the song. No composer is named for either.

The castle at Redcastle (near Beauly in north-east Scotland) has been derelict for about 200 years, but I think they used to hold a piping competition there in the late 19th century, and I vaguely remember the tune relates to a celebrated piper of the time who competed there. There is also a 6/8 march "Redcastle" which is completely unrelated to "Campbell's Farewell".