Musket
Martin "Waterman" Carthy married Norma Waterson. Get it now?
His training, by the way, started as a boy chorister in the Chepel Royal - and then he moved to work with Leon Rosselson in the mid 60s.
On the subject of counter tenor, much of the folk repertoire goes right there. It was born in exactly the same circles as sponsored the real castrati, the likes of Farinelli. It starts with Samuel Pepys learning the recorder (always thought that was a reference though to fingering his inflatable pipe, but no...). The whole idiom is riddled with attempts to reach out to the common woman (all these blithering milkmaids being typically champetre straight from Versailles). We even have a number of kinstruments - the hurdy, for example - which would have died if they hadn't been adopted by those circles.
So we might twist the question to point out that the need to classify the corpus as "folk" comes from people who were not "folk". If they were, they would just be "our" songs - as is the case in the Suffolk/Essex tradition. So perhaps the answer is that ONLY posh people sing Folk Songs, normal people just sing and don't give a damn.