I knew Nadia a little during the sixties. She, Sidney Carter, Donald Swann and I did some TV and folk places together in Edinburgh.
I only once heard her sing "Red and Green Christmas" and it haunts me still (though I can't remember the tune or words!). So far as I recall "Port Mahon" was writted be Sidney (who also wrote "Down Below", and "Lord of the Dance". Nadia sang it like magic.

She was a fine person and beautiful singer. Very happy to hear of her again.