My copy of The Roving Songster doesn't have that intro, and it doesn't have any indication which of the songs are John Brune's. I think this is one though, to lighten the tone:

The Last Drop in the Bottle

Tis the last drop in the bottle
And I'm left blooming well alone.
All my lovely companions
Without me to the pub have gone.
Sic transit gloria mundi
Mundi gloria it makes me sick
How the world is all cupboard lovers
Slow giving but taking quick.

I'll not leave thee, thou lone one
To evaporate away
There'll be not a drop left in this bottle
By the end of this dreary day
I will mix thee, rum, with honey,
Demerara sugar, tea and lemon juice
And tonight we'll be right chummy
Me and my last drop of booze.

Try singing it to the tune of The Last Rose of Summer...