I note in this piece about the Master from the Dungarvan Museum in Co Watrford, near where he came from, that both spellings are used. That's the way to do it.

It's an interesting story on the end of that link too - about how he nearly got drowned when he went thropugh the ice on a river at the Waterloo Cup in 1870, but got saved by a hero called Michael Wilson, and retired to stud. A happy ending. (And about his visit to meet Queen Victoria.) But in deferance to Joe and the Cut and Paste business, I'll just leave the link to it.

But there ought to be a song about the Master's last run. Perhaps there is.