From the notes to the Penguin Book (1959):

"The theme of this ballad is banal enough: a triangular love-affair that ends in the death of all three lovers.  It is the characters that hold the imagination -weak, fickle Lord Thomas, haughty, fair Eleanor, and the dark, vengeful bride with the dagger hidden in her wedding dress.  During this century the ballad has quite frequently been found over an area bounded by Devon, Hertfordshire, Hereford and Staffordshire.  Also several Scottish sets are known.  It is interesting that most of the English versions, and all the numerous American ones, obviously derive from a broadside text published during the reign of Charles II and often reprinted.  Scholars incline to consider oral transmission to be almost a sine qua non of folk song diffusion, but ballads such as this remind us that word-of-mouth is far from being the only way in which folk songs have been traditionally passed on.  In Scotland this ballad is sometimes called Fair Annet.  It must be said that some of the Scottish oral versions hold beauties lacking in the texts under influence of print: such, for instance, as this embellishment to the description of Annet's grand journey to Lord Thomas's wedding:

There were four and twenty gray goshawks
A-flaffin their wings sae wide,
To flaff the stour* fra aff the road
That fair Annie did ride.

*(Stour= Dust, or a cloud of dust)

In the version of the text printed here, Mrs. Pond's words have been expanded from versions collected by Hammond from Mrs. Rowell, of Taunton, Somerset, in 1905 (FSJ vol.II, p.105) and by Sharp from Mrs. Cockram, of Meshaw, Devon, in 1904 (FSJ vol.II, p.107).  Other versions have been found in oral tradition in Hampshire (FSJ vol.II, p.106), Somerset (FSJ vol.II, p.109), Hertfordshire (FSJ vol.V, pp.130-1), Staffordshire (English Folk Songs, ed. C. Sharp, 1921, p.651), and Gloucestershire (Folk Songs of the Upper Thames, ed. Alfred Williams, 1923, pp.135-7). Kidson (Traditional Tunes, 1891, p.40) reports a Yorkshire version with words from a broadside of c.1740. "  -R.V.W./A.L.L.

This version was collected by Cecil Sharp from Mrs. Pond of Shepton Beauchamp, Somerset, in 1904, and was first published in the Folk Song Journal, vol.II, p.107.

Other versions on the DT:

Lord Thomas

Lord Thomas and Fair Elender (The Brown Girl)

Lord Thomas and Fair Ellender

In the Forum:

Lord Thomas and Fair Annie

Lord Thomas and Fair Ellender  (with guitar chords but no tune)

Who WAS The Brown Girl?  (Discussion)

Child #73
@marriage @murder @love @family @suicide

There is a version at Lesley Nelson's  Child Ballads  site:

Lord Thomas and Fair Ellinor

There is an entry at  The Traditional Ballad Index:

Lord Thomas and Fair Annet

There are quite a few broadside copies, showing little textual variation over 150 years or so, at  Bodleian Library Broadside Ballads.  Of those in legible state, these are perhaps the most interesting:

A Tragical Story of Lord Thomas and Fair Ellinor  Printed in 1677 "for F. Coles, T. Vere, J. Wright and J. Clarke, 1677. License note: This may be Printed, Dec. 13, 1676, Ro. L'Estrange".

Lord Thomas and fair Eleanor, with the downfal of the brown girl  Printed between 1761 and 1788 by Thomas Saint, Newcastle upon Tyne.

A tragical ballad of the unfortunate loves of lord Thomas and fair Eleanor; together with the downfall of the Brown girl  Printed between 1780 and 1812 by J. Evans, No. 41, Long-Lane, London.

A tragical ballad of the unfortunate love's of lord Thomas and fair Eleanor  Printed between 1802 and 1819 by J. Pitts, No. 14, Great St. Andrew- Street, Seven-Dials, London.

Lord Thomas and Fair Eleanor with the Downfal of the Brown Girl  Printed in 1811 by Thos. Evans, 79 Long Lane Wt., Smithfield, London.

Lord Thomas and Fair Eleanor  Printed between 1813 and 1838 by J. Catnach, Printer, 2, Monmouth Court, 7 Dials, London.

These are large images.

Malcolm