Fenian, I might have found a cousin to the song you are looking for, for my version is not about the R.U.C, but about the Special Branch. These songs come and go, for they are easy to accommodate to any new target group. My guess is that the song you are looking for is identical to this one but for two or three lines. My version comes from Songs of Resistance, 1968-1975, a Sinn Fein outlet. No author is given, of course, and the tune is (fine job, Joe): "The man that waters the workers' beer." The Slimey Man

1. Oh, I'm the man, the slimey man, that listens at yer door
for I belong to the Special Branch and that's what I'm paid for,
if your [sic] singing songs of protest or against repressive law
I'll put yer name in me book and by hook or by crook I'll see that you're done for, I'll see that you're done for.

2. If you're red, pink or Republican or belong to the P.D.
I'll terrorise your parents to save democracy,
I'll tell your boss to sack you and I'll never shed a tear
for I like my job with the Special Branch at [pound sign] 5000 a year.

3. Oh, the craven and the cowardly, they cannot be absolved,
they do the work of the Special Branch and say they're not involved.
At Buchenwald and Belsen they said they weren't to blame,
but at the court of Nuremberg they were sentenced just the same.

4. Oh now Dublin life is changing and changing very fast.
The youth are moving forward and learning from the past,
when Ireland is united and the workers have control,
there'll be no need for the Special Branch so we'll make them shovel coal.

A personal note: Whatever despisable actions the Special Branch may have done (or not; I don't know enough to judge), the comparison to the Nazi concentration camps' crimes (verse 3, line 3) is unwarranted, in my eyes.
Wolfgang