Is it this one? (I'm at work and can't see the video)

This song was written by John Davy (around 1818) for the finale of his opera, "Rob Roy". It was written to the old tune "Duncan Gray".

Pardon now the bold outlaw
Rob Roy MacGregor, O!
Grant him mercy, gentles, a'
Rob Roy MacGregor, O!
Let your hands and hearts agree
Set the highland laddie free
Let us sing wi' muckle glee
Rob Roy MacGregor, O!

Lang the state has doomed his fa',
Rob Roy MacGregor, O!
Still he spurned the hatefu' law,
Rob Roy MacGregor, O!
Scots can for their country dee;
Ne'er frae Britian's foes they flee,
A' that's past forget - forgie,
Rob Roy MacGregor, O!

Scotland's fear and Scotland's pride,
Rob Roy MacGregor, O!
Your award must now abide,
Rob Roy MacGregor, O!
Lang your favours hae been mine,
Favours I will ne'er resign,
Welcome then for auld lang syne,
Rob Roy MacGregor, O!