John Ker, third Duke of Roxburghe, was born on the 23rd of April 1740 in Hanover Square, London. He was the elder son of Robert Ker, second Duke, and on the death of his father in 1755 succeeded to the title and estates. While on a tour on the Continent he became greatly attached to Christiana, eldest daughter of the Duke of Mecklenburg-Strelitz, and there is little doubt that she would have become his wife had not King George III. soon afterwards sought the hand of the Princess's younger sister in marriage, when it was considered necessary to break off the match, partly for political reasons, and partly because 'it was deemed indecorous that the elder sister should be the subject of the younger.' This was a great disappointment to both the Duke and the Princess, who evinced the strength of their affection by remaining single during their lives. George III., probably feeling that he had done the Duke an injury, always manifested a warm friendship for him, and bestowed upon him various appointments in the royal household. In 1768 he was made a Knight of the Thistle, and in 1801 was invested with the Order of the Garter. He died on the 19th of March 1804.

The Duke, who was remarkable both for his fine presence and his mental accomplishments, collected a magnificent library at his residence in St. James's Square, London. It contained among numerous other treasures the famous Valdarfer Boccaccio, upwards of a dozen volumes printed by Caxton, and many from the presses of Pynson, Wynkyn de Worde, Julian Notary, and other early English printers. The first, second, and third Shakespeare folios were in the collection, as well as a large number of early quarto plays. The library was especially rich in choice editions of the French romances, and in the works of the English dramatists who flourished during the reigns of Elizabeth and James I. Some rare books printed in Scotland were also to be found in it. The collection of broadside ballads in three thick folio volumes, now in the British Museum, is perhaps the most extensive and interesting ever brought together. It was begun by Robert Harley, Earl of Oxford, from whose library it passed successively to those of Mr. James West and Major Thomas Pearson, and at the sale of the books of the last-named collector it was purchased for thirty-six pounds, four shillings and sixpence by the Duke, who made many additions to it while in his possession. The collection has been admirably edited by Mr. William Chappell and the Rev. J.W. Ebsworth for the Ballad Society. Other books deserving special notice were the first edition of Pliny, printed by J. de Spira at Venice in 1469; Cicero's EpistolÆ ad Atticum, etc., printed at Rome in 1470; the 1580 edition of the Paradyse of Daintie Devises, and the first edition of Shakespeare's Sonnets.

Among the manuscripts the most valuable were Chaucer's Canterbury Tales, bound with Lydgate's Life of St. Margarete, on vellum, with illuminations, and the Mystere de la Vengeance de Nostre Seigneur, also on vellum.

The library was sold in 1812 by Mr. Evans of Pall Mall in the dining-room of the Duke's house in St. James's Square, and the total amount realised was twenty-three thousand three hundred and ninety-seven pounds, ten shillings and sixpence. The sale, which consisted of nine thousand three hundred and fifty-three lots, lasted forty-two days, commencing on the 18th of May, and ending on the 4th of July. It was followed by a supplementary one of seven hundred and sixty-seven lots, which began on the 13th of July, and lasted till the 16th of the same month. The catalogue was compiled by Mr. George Nicol, bookseller to the King. The sale excited very great interest; and Dibdin, who gives an account of it in his Bibliographical Decameron, tells us 'the room was so crowded that nothing but standing upon a contiguous bench saved the writer of The Bibliographical Decameron from suffocation.' The prices obtained for the books were very high. That 'most notorious volume in existence,' the Valdarfer Boccaccio, which cost the Duke of Roxburghe but one hundred guineas, was acquired by the Marquis of Blandford, after a severe struggle with Lord Spencer, for two thousand two hundred and sixty pounds, and Dibdin says that the Marquis declared that it was his intention to have gone as far as five thousand guineas for it. A copy of the Recuyell of the Histories of Troye, which once belonged to Elizabeth Grey, wife of Edward IV., was purchased by the Duke of Devonshire for one thousand and sixty pounds, ten shillings; while three other books from the press of Caxton, The Mirrour of the World, the Fayts of Arms, and Gower's Confessio Amantis, sold respectively for three hundred and fifty-one pounds, ten shillings, three hundred and thirty-six pounds, and three hundred and thirty-six pounds. The collection of ballads fell to Mr. J. Harding for four hundred and seventy-seven pounds, fifteen shillings. At the sale of Mr. B.H. Bright's books in 1845 it was secured for the British Museum for the sum of five hundred and thirty-five pounds. The first folio of Shakespeare's Plays fetched one hundred pounds, and his Sonnets twenty-one pounds. The two manuscripts mentioned realised three hundred and fifty-seven pounds and four hundred and ninety-three pounds, ten shillings.

A dinner was given, at the suggestion of Dr. Dibdin, to commemorate the sale of the Boccaccio; and Earl Spencer, Dr. Dibdin, and other bibliophiles met on the day of the sale at St. Alban's Tavern, St. Alban's Street—now Waterloo Place—and then and there formed the Roxburghe Club; Earl Spencer being the first President.