Actually Hawker did NOT write the original:

"Except for the refrain, the exact original words of the song are lost. Those given here are based on a 'restoration' written (c.1835) by the Rev. R.S. Hawker, of Whitstone, near Stratton, who died in 1875. In 1688, the Trelawney Song is said to have resounded in every house, in every highway, and in every street in Cornwall."

This comes from the Cornish Song Book, 1929, along with three versions of the song, one in Cornish language written by Henry Jenner.