Who was Vaughan Williams' friend who helped collect folk songs in southern England and was a founding father of the folk-song revival in England in the early 20th century?
Fantasia on Christmas Carols:  First performed at the 1912 Three Choirs Festival at Hereford Cathedral, the work is a single movement of roughly twelve minutes which consists of the English folk carols "The truth sent from above", "Come all you worthy gentlemen" and "On Christmas night all Christians sing" (i.e. the Sussex Carol), all folk songs collected in southern England by Vaughan Williams and his friend Cecil Sharp a few years earlier. Cecil Sharp: Cecil James Sharp (22 November 1859 – 23 June 1924) was the founding father of the folk-song revival in England in the early 20th century.
Cecil Sharp