Byron gave it to his childhood sweetheart, Elizabeth Pigot, who lived near his Newstead Abbey home in Nottinghamshire.
Peter Beal of Sotheby's has come across several locks of hair - including Byron's (three examples), Nelson's and Wellington's - but he has taken few of them seriously without clear supporting evidence. This one, he explained, is different: it has come straight from Pigot's family.
It dates from 1807, when Byron (then 19 and a student at Trinity College, Cambridge) and Pigot, six years older, 'were going strong together in an innocent way', Dr Beal said. It was a token of a friendship unlike all others in the great philanderer's life, a man who was to be attacked for his bisexuality and accused of incest with his half-sister. His innocent relationship with Elizabeth was very different from the sexual initiation he is said to have received from two of his nurses, the romantic attachment with younger boys at Harrow and the string of passionate affairs with women, including the married Countess Guiccioli.
The Pigot household became a home from home for him. Although a close friend of John Pigot, a medical student at Edinburgh, there was a particularly tender intimacy with the sister, Elizabeth. She became his confidante: it was to Elizabeth that Byron confided his infatuation with a choirboy at Trinity Chapel, writing in a letter of 1807: 'I certainly love him more than any human being.'
It was Elizabeth who helped transcribe the manuscript for Byron's first book of poems, Fugitive Pieces, published privately. It was with Elizabeth that Byron exchanged books. They wrote verses to one another: among a number of other items from Pigot's family in Sotheby's sale is a verse written to Byron by Elizabeth in 1806: '. . . Thou may'st believe me when I say,/That Friendship's bright unchanging ray/Beams from my heart uncheck'd & free',/And, Byron] it shines full on Thee'. They were written in a book of poetry given to her by Byron with the dedication, 'Eliza Pigot . . . L'Amitie est L'Amour sans Ailes' (Friendship is Love without Wings).
Among a large number of collectors expected to show interest in these lots at Monday's sale are members of the Byron Society.
Derek Wise, an antiquarian bookseller and chairman of the Byron Society, estimates that there are around 1,000 members world-wide. There are two British societies, the Byron Society and the Newstead Abbey Byron Society, with representatives in more than 30 countries. Many of them are at Nottingham University this weekend for the annual Byron conference.
Last summer, a lock of Byron's hair, given in 1805 to a schoolfriend, sold for pounds 4,620 to a private collector.