'Jack Orion' was written by A L (Bert) Lloyd. He based it on the plot of the old ballad 'Glasgerion'. This is common knowledge among people who read sleevenotes; he made no secret of it. He set it to the tune Andy Stewart wrote for his own song 'Donald Where's Your Trousers'. That is less well-known (though Bert did tell people on occasion), but it's obvious if you think about it.