According to the Internet source given below, Margaret "Peggy" Seeger is an American folk singer who has lived in Britain for more than 30 years and was married to Ewan MacColl
until his death in 1989.
Along with other left-leaning singers such as Paul Robeson
during the McCarthy era she had her US passport withdrawn and finally settled in Britain. There she playied a part in the English folk music revival. As such Seeger was a leader in the introduction of the concertina in English fol. While not the only concertina player, her "musical skill and proselytizing zeal ..." was a major force in spreading the gospel of concertina playing in the revival.
After Ewan MacColl's death she eventually returned to USA in 1994.
||Biography by wikipedia.org.