Plumber, here's a song from the Battlefield Band Songbook. I'm not sure if it is the one you are looking for, but it is worth posting anyway.

LADY KILMARNOCK'S LAMENT
(trad., music: Alan Reid)

Oh hawthorn tree, sweet hawthorn tree how oft I've watched thee bloom,
and left the fairest flowery lea to hail thy sweet perfume.
But where is he I used to meet beneath the drooping shade,
while softly fell the dewy scent upon his Lowland plaid.

Kilmarnock sought me for his bride, a noble brave and free.
What was a jewelled crown beside the love he gave to me?
I loved and was beloved again no blyther bride could be,
but now in sorrow I remain beneath the hawthorn tree.

Oh hawthorn tree, sweet hawthorn tree no more I'll hear him sing,
the loyal songs he sang to me on Scotland's royal king.
My lord upon a scaffold fell for Scotland and for me,
so here I lie just like to die beneath the trysting tree

It is believed that Lord Kilmarnock fought in the first Jacobite rebellion and was hanged in London.
Wolfgang