Quite shamefully I omitted to say that Google also gave numerous references to the Tom Napper - Tom Bliss version so it was especially kind of Tom B to post the words. The version that I remember, possibly altered by time:-

On the first day of April I'll never forget,
How two Irish sportsmen together they met,
Called for a drink and then swore solomnly,
That they'd play a trick on the first one they'd see,
Laddie fol de riddle i do,
Right fol the rol dee.

On the road they had not been but for a short while,
When Campbell the Rover came by in great style,
They bid him "Good Morning" he bade them the same,
And in close conversation together they came

The came to an ale house and made a full stop,
And asked Campbell in for to take a wee drop,
Acepting the offer Campbell replied,
"I'll have a wee drop just to wet my inside"

A bottle of whiskey they poured down their throat,
Then the Irishmen got up to bale out the boat,
Leapt on their horses and galloped away,
Leaving Campbell the Rover the reckoning to pay

Never mind now dear landlord Campbell did say,
I've got plenty money the reckoning to pay,
But if you'll permit me before I do go,
I'll teach you a skill that perhaps you don't know

I'll show you a trick that's contrary to law,
How two kinds of liquer from one barrel can draw,
The landlord being eager to learn of the plan,
Straight to the cellar with Campbell he ran

Into the barrel he bored a small space,
Saying "Landlord put your left thumb in this place",
Boring another said"put your other thumb there,
While I for a tumbler do run up the stair"

He rushed out the ale house without more delay,
Leaped on his horse and he galloped away,
Leaving the landlord to think on the way,
How Campbell the Rover the reckoning did pay