You just do not hear enough about Robin Williamson these days, years. Here's his and his partner Bina's page. That site directs you here to find old albums, including the one this song is from, 1981's Songs of Love and Parting:
Originally released on the Irish Claddagh label in 1981, 'Songs Of Love And Parting' was Robin's first solo album after the amicable demise of the Merry Band. All songs were written by Robin (with a few traditional tunes thrown in for good measure!) and are now regarded by many as his finest compositions.
The album contains the classics 'For Mr Thomas' (a tribute to the Welsh Bard), which was later covered by Van Morrison, 'Fare Thee Well Sweet Mally' and 'Flower Of The Briar'.
"For Mr. Thomas":