Having listened to Bayard again I think that Col Dryden's melody is original- and not derivative. Col Dryden's bass notes- so essential to the song- are absent from ' I saw her as she came and went 'which also doesn't flow as lyrically as Colin's song.   I think that a large part of the enquiry will be answered by discovering if Dominic Behan's shortening of the poem differs from Col's. If it does then that's proof enough for me that Col Dryden's ' Reading Gaol ' is his own work.
Nice to read you all   :) xx