Does anybody remember a notorious episode of The Magic Roundabout in which Dougal told Brian Snail to bugger off? It was on c.early 1976- Dougal was arguing with Brian and swore thus at him. Apparently the culprit was a BBC sound engineer who'd recently been made redundant, and was getting back at his employers.
It all sounded perfectly in line with the dialogue, there was no change in accent or voice tone. It didn't even surprise me, since Dougal was so boorish and rude, and Brian such a little upstart, that it sounded like the sort of thing that he WOULD say to him! It was all over the 'papers the following day though.