Hi, Bearheart - this page (click) has a review of a Black Family performance. The review says that "Sweet Liberty" was penned a century ago by Portadown’s John Shields.

Here's a Black Family recording:

https://www.youtube.com/watch?v=pMHNLSnQE64

Apparently, Shay Black was a member of the five-member Liverpool group Garva, which recorded the song as "The Prayer of Shields."

I found a review that says "Shay (Black) leads the up-tempo "Prayer of Shields," written by a 19th century Portadown linen weaver, it was written to promote harmony amongst peoples." (http://www.library.folknorthwest.co.uk/FNW%20V28%20Iss1%20Summer%202005.pdf - page 38)