Felix de Marez Oyens, European department head for books and manuscripts, described it as 'one of the most desirable books in English literature'.
Of a few hundred copies that were printed, 18 are known to have survived; only two - including an example in the British Library - are complete. Christie's example is missing seven of the original pages. Otherwise, though it has obviously been read, its condition is excellent. That is unusual for Caxtons: Mr de Marez Oyens said that 'as he mostly printed in the vernacular, they were read more than Latin books'.
Indeed, the book - printed in Bruges in 1473, three years before Caxton established himself in premises near Westminster Abbey - includes a postscript by Caxton which reads that it is 'not written with pen and ink as other books so that every man may have them at once'.
Today, although available in a modern edition, readers of this romantic history of the various destructions of Troy has dwindled to a few scholars. As the opening line conveys, it is not an easy read: 'here begynneth the volume intituled and named the recuyell of the historyes of Troye, composed and drawen out of dyverce bookes of latyn into frensshe . . .'
This copy has been among the 43,000-volumes in the library at Longleat House, the Wiltshire home of Lord Bath. According to Michael Chantler of the solicitors Farrer & Co, a further 18 books from the library will also be auctioned. All are duplicates. The other copy of the Caxton was owned in the early 16th century by Sir John Thynne, the builder of Longleat.
The books are being offered for sale under the terms of the will of the 6th Marquess of Bath who died last June. The sale is to provide for his family rather than the estate.
Richard Linenthal, a director of Bernard Quaritch, a leading antiquarian dealer, said: 'This has been a great book for hundreds of years. It's a seminal book in the English language. It merits a high price.' That it is not a unique copy, he added, did not diminish its importance.
Christie's yesterday broke the record for Caspar David Friedrich, the German Romantic artist, when it sold Walk at Dusk for pounds 2.3m (estimate, pounds 2m). It will be going to the Getty Museum in Malibu, California. Friedrich's previous record was pounds 1.5m, set in 1987.