No doubt Carthy is superb, but if you are going to make a link with UK and American folk traditions, Lonnie Donegan in the 1950's, probably had the greatest impact on British popular and folk music, with his introduction of the works of Leadbelly and Woody Guthrie and the subsequent start of Skiffle bands. He got the UK looking at other sources besides their own and in 1977 did a recording of Rock Island Line with Rory Gallagher on guitar, on the Album Putting On the Style, that probably paved the way for Steeleye Span's use of the electric guitar in the folk song genre.