Haven't seen the concert but we saw them live and close up in a university common room concert back in 1964/5 and they still stood close together and sang as one.
Two mics?
Luxury!
Groups around here were lucky to get one working mic between them!
Later my tastes moved away from the PP&M type of song but looking back now, they were truly professionals and were very important to the folk movement at the time and to me personally.
Robyn