In 1972 he released his first record, "The Green Album", on Westwood, a small label. With scant publicity or promotion, the album made little impact and only 500 copies of the record were pressed. Hennessy returned to labouring on building sites in the UK and did not release another album for twenty years. When he did, his 1992 release "The Rehearsal" outsold U2 in Ireland, eventually attaining triple platinum status. His following albums, "A Year in the Life" and "Box" also sold extremely well in Ireland.