VOLUNTEERS at Tavistock?s Oxfam store thought they had discovered the key to a fortune this week when they found a letter which appeared to have been written by the Romantic poet Lord Byron. The letter was lodged inside an 1828 edition of his works, published in Paris. In the poet?s handwriting and signed by him, it had all the hallmarks of the genuine article . . . Alas, when the volunteers carried out further research, they discovered that, though rare, the letter is well known in the book-collecting world as a mechanically printed facsimile. Both the book and the letter were published without the poet?s consent. The letter, often detached from the book, has been known to go on sale as genuine. For the time being, the letter will remain on display at the North Street store until the volunteers decide how best to sell it. Lord Byron, born in 1788, was a leading figure in Romanticism. Among his best-known works are the narrative poems Childe Harold's Pilgrimage and Don Juan. He joined freedom fighters in Italy and Greece before his death from fever in 1824. He had an intense love affair with Lady Caroline Lamb. who famously described him as ?mad, bad and dangerous to know?.