"Note: MacColl based the tune on that of a Scots traditional ballad, "The Famous Flower of Serving Men."
I haven't gone into this at all, but Peggy told me that, certainly around the time of the Radio Ballads 'Famous Flower' (listed under 'Sweet William' in Last Leaves of Tradional Ballads, was one of Ewan's favourite tunes and he used it for a number of songs (never been able to discover which).
One of his practices with a new song was to choose a tune that might fit and wander around the house whistling it, making small changes until he arrived at a satisfactory form.
I saw him do this once while he was writing the 1968 Festival of Fools; I was trying to carry out some electrical work and he nearly drove me bloody demented with his 'under-the-breath' whistling.
Jim Carroll