I happen to have the programme here for the Tupholme Manor Park Concert on 24th July 1971 and the headline acts seem to be James Taylor and Tom Paxton, though Buffy Sainte-Marie does get the first wrote-up in the programme. Swarbrick and Carthy finished the concert.

Roy Hollingworth and Andrew Means, writing in "Melody Maker" said:
[Begin quote]
Its four years since Buffy Sainte-Narie played in Britain but from her reception one could have imagined her to be a countrywide favourite. As her annoucner tolled off the details of her four year absence, someone volunteered "We missed you". It set the mood of her performance - the emotional greeting of old friends "Say 'I love you'" Buffy instructed the obedient crowd. Further instructions did not arouse the same willing execution . In any case her impact was at its greatest when she was singing rather than influencing the relationships of the gathering. Opening on the familiar note of "Universal Soldier" she progressedinto an expolitation of the vibrating earnestness her voice contains. She is an able representative of her people, the Red Indians, and few can put their case as a downtrodden nation better, as in her film theme "Soldier Blue". [End quote]

I'm sorry to say that by the time she came on the concert had run so late that we were tripping through a muddy field trying to find our way back to the bus for Lincoln, so we could miss our train back home and spend the night in the bus station, waiting for the first bus of the morning.