Odd
I'd not heard of this before, and presume it would have been around 1985/86 (when Louw & Mordt both switched). The article mentions Danie 'Doc' Craven asking Gerber not to switch - from what I can gather, Craven's approach wasn't so much politely asking, as ranting about being traitors to the amateur ethos and rugby union.
Thanks for the link.
I remember it very well and had a cutting from the Daily Mail for many years entitled 'Saints to step up Gerber chase'. It was indeed the season after Mal Meninga and interestingly enough the aforementioned Danie Craven had a bodyguard for a short while back in the 1950's, the one and only KT Van Vollenhoven.