An "outstanding" collection of illuminated manuscripts previously owned by kings, bishops and the aristocracy is expected to fetch up to £16 million when it goes under the hammer.
The private collection, which Christie's described as the most valuable of its kind ever to be offered at auction, includes the personal prayerbooks of King Francois I of France and Elizabeth de Bohun, great-grandmother of King Henry V of England.
The Arcana Collection: Exceptional Illuminated Manuscripts And Incunabula, which has a total estimate of between £11 million and £16 million, will go on sale in July.
But the sale is just the first part of the auction and more works which are currently being valued are expected to be offered to bidders over the next 18 months.
The manuscripts are owned by an anonymous American collector, who spent three decades amassing the prized items.
The illuminated manuscripts are handwritten books with illustrations and decorations painted in brilliant colours and gold.
Books Of Hours - prayerbooks intended for private use - were the most popular type of illuminated manuscript and their appearance could be tailored to an individual's taste.
Margaret Ford, head of books and manuscripts at the London auction house, said: "This is a truly exceptional collection... They are masterpieces of medieval and Renaissance art, many commissioned by important patrons.
"Books Of Hours are among the most personal artworks. Used for private devotion, they were also intended to reflect the wealth and status of the owner and leading artists and craftsmen were engaged in their creation.
"The Arcana collection offers the best examples of their type, ranging from Books Of Hours to works of literature and on the natural world.
"The beauty of the page is often complemented by the importance of the text, exceptional, original condition, and interesting, even highly distinguished, subsequent ownership."
She said of the collector: "It has been the aesthetic aspect of these masterpieces which has appealed in particular to this private collector and excited his curiosity to acquire and learn more about them.
"A successful businessman, he has also generously supported public institutions with holdings in this field."
Highlights of the collection include:
:: A Book Of Hours illuminated for King Francois I of France, expected to realise £300,000 to £500,000.
Francois is described as one of the greatest princely patrons of the Renaissance. Leonardo da Vinci spent his final years in the king's service. After his death Francois acquired The Mona Lisa from the artist's estate.
:: The Hours and Psalter of Elizabeth de Bohun, Countess of Northampton and great-grandmother of King Henry V of England, are expected to realise £2 million to £3 million.
These were lent by a previous owner, William Waldorf Astor, to the important loan exhibition in New York 1883 which raised funds for a pedestal for the Statue of Liberty.
:: A manuscript Bible produced in Italy in the middle of the 13th century.
It appears to have been made for the use of a convent of Dominican friars and carries an estimate of £2.5 million to £3.5 million.
The manuscripts will also go on public exhibition for the first time, between July 3 an 7, alongside Christie's auction of Old Masters and 19th Century Art.
The collection of 48 lots will go under the hammer on July 7 in London.