Thanks to all those who have chipped in with suggestions and links. This is only my second time using this site and I'm really blown away by the amount of goodwill and help that's available out there.

The ",and" link on Masato's first contribution leads to a melody which fits the Byron words very well. On the other hand, the tune which I have half-learnt from the various pipers' recordings doesn't seem to suit those words at all comfortably. So is there an entirely different poem (possibly in Gaelic) set to the tune which Irish pipers play?

I've tried to play the CD clips mentioned under the first link in the same contribution from Masato, but unfortunately can't get them to play on my PC. I have the Sean Keane album and it contains the tune which I know, so I wonder if the other two recordings feature the same tune or a different one.

Incidentally, the mother of all the pipers' versions is probably a Willie Clancy recording which I also have, and this would be consistent with the suggested provenance via Scottish sappers in Clare. It's also the one in which the phrasing seems most credible, but it's still pretty tricky given Clancy's very personal style.

The photographs on the hillwalker site explain the Mountain/lake question raised by Steven: the Loch is a corrie below the summit.

There's a similarly-named manmade feature of sad memory (Lochnager Crater) here in Belgium, where I currently live. It's a water-filled crater resulting from the detonation of an enormous mine which was set off under the approaches to the Messines Ridge in Flanders during the first world war. If I remember the story correctly, the detonation was slightly delayed and a large number of Scottish troops, who were due to advance after the explosion, were killed because it was assumed that the mine had failed and they had already begun to advance when it went up.

And finally, may I reassure our English friends that, in spite of the weird ranting exchange going on in another string under the title "Bloody Sunday" (what's that doing on this friendly site?) and also in spite of last Saturday's cruel treatment of my compatriots by the England rugby team, I'm not trying to stir up anti-English sentiment!