The discovery of this "Rule Hibernia" MS seems so surprising you might think it's a hoax, but it really does seem the real thing, and in 1720 it is certainly twenty years before Arne's "Rule Britannia". And the fact that Carolan's "Planxty Reade" is on the next page of the notebook is a clincher, given that "Rule Britannia" is really only a variation on it. It's quite funny really.