The Furey's have also done it as have the Corries, and Jack (John? something) Murphy (This was on a 7" I was once lent to learn the song on the flipside and I never took a lot of notice of the singers name). Other title is why Murphy is not at work today. And they all say Pat Cooksey as the source so I guess you can date it somewhat by that if you know when he was writing.
I seem to remember Hoffnung doing it as a letter, or at least something similar. That is of course if you all know Hiffnung, the English comic/after dinner speaker, who was famous for reading "letters" he had received or been given.