June 1967, at the 3rd Wellington Folk Festival (in NZ), a group sang Wild Mountain Thyme, unaccompanied, in multi-part harmony and it was a WOW! moment.
In fact, that was when I switched from singing mainly American folk to actively searching for more British unaccompanied songs.
Then we discovered the Watersons, the Young Tradition and the rest, as they say, is history.
Robyn