Trewissick.
The book has no background on any songs and I don't know any except that as the song was written in an Exercise Book on page numbered 77 it is called Exercise 77. But I'll try and find out and come back. On several occasions last and this year Martyn and Graeme did a folk club night together. Martyn singing exclusively Graeme's songs for his second set while Graeme on stage too would tell the audience the scenario of the song or its writing. I was fortunate to get to some of these which were great nights and many floor singers chose also to do songs by Graeme. There is a further book, 'Forgotten Songs Remembered' which was launched at the Grove on the first of the nights described. If you search for the Folk Leads website it'll be deep in there somewhere.
John