G'day,
This is Child Ballad #251. The DT has only one version. It appears to be the Martin Carthy version with errors. e.g. first verse:

Now Long John's from the mountain gone, He's to London town.
And the king's daughter in fair London, she fell in love with him.
Now Long John was a giant born. He was fourteen feet in height
And the king's daughter, she wept for him as she laid alone at night

Cheers,
Alan