As indicated, Behan used the song, a verse at a time, in between the acts. There's often other "business" going on - the guard making comments about the singer's noise, etc.

The exact verses are slightly different from the way MacColl & most others later sing them. He _may_ have been the first to record it.

I got interested in the "proper" accent to use. Often it's sung in bog Irish or (more appropriately) prison/street slang, with which Behan would have been very familiar.   The song is written in standard English. The book gives no info on the accent to be used or social class of the singer. Well, other than his current situation.

I tried to get hold of an original recording. Turned out (this is mostly anecdotal & newspaper reporting...) the play was first produced in a miniscule theater(re) on zippo budget. To save on salaries, the singer is never seen. He sings from his cell only and is, in fact, a tape recording of Behan, himself.

The tape was stored with play paraphernalia and ultimately just disappeared. Gone. Zap. Seems that's pretty definitive. I'm told.

A shame. There is no credit (or disclaimer) in the book as to authorship.