It's called Champion, He Was A Dandy and the chorus is...

Champion, he was a dandy
Till Murphy, that dirty old sod,
Came along with his black-and-tan terrier
And murdered me twenty pound dog.

I would give you the verses too but I don't know them. This is a popular song from, I guess, the first 20 or 30 years of last century. Bob Davenport, as I recall, recorded this in the 1970s for Leader/Trailer. At least you have the title now. Good luck.

All the best,
Dan