I agree with Susanne, if Robin's friends just heard him whistling the tune, they's have probably assumed it was "Roddy MaCauley" - so was there any chance that he was the one that Robin's colleagues thought was "a poofter". On the other hand, if South was a rather detached, accademic type, that might have been the sort of opinion that a building site "Mick" would have had of him.