I have just come across Master McGrath in your DT. This is the Dominic Behan version, I heard Dominic sing it on a few occasions when he paid a visit to my neighbour, the late Malachy McGurran. That Behan version is never sung around Lurgan. The original song is in Colm O Lochlainn's Irish Street Ballads. The second verse, missing in Behan's version notes the Town of Lurgan:

On the twelfth of December that day of renown,
McGrath and his keeper they left Lurgan Town,
A gale in the Channel it soon drove them o'er,
On the thirteenth they landed on fair England's shore.

Slan Ard Mhacha.