Treasure united with the page it lost 500 years ago

It was a book of such value that its illuminated pages were stolen - to be lost for more than 500 years - before the manuscript could even be bound in the 1490s. But yesterday, the Sforza Book of Hours, one of the most outstanding treasures of the Italian Renaissance, was intact again after the last surviving leaf was fitted into the jewel-like manuscript.

It was a book of such value that its illuminated pages were stolen - to be lost for more than 500 years - before the manuscript could even be bound in the 1490s. But yesterday, the Sforza Book of Hours, one of the most outstanding treasures of the Italian Renaissance, was intact again after the last surviving leaf was fitted into the jewel-like manuscript.

For centuries, those misappropriated pages seemed lost for ever. There was certainly no suggestion the missing pages might ever be found when a Scottish collector and connoisseur, John Malcolm, gave the main body of the book to the British Library (then the British Museum) in London in 1893.

But over the past 63 years, three leaves came to light that scholars identified as belonging to the stolen portion.

Yesterday, the last of these pages was publicly reunited with the Sforza Hours, bringing to a close a nerve-racking attempt by the library to purchase what they saw as the final piece of the jigsaw. It had raised £191,000 inside a month to stop the page being sold by an American dealer into the hands of a private collector.

The Sforza Book of Hours manuscript was painted in about 1490 by a famous court artist, Giovan Pietro Birago, for Bona of Savoy, the widow of Galeazzo Sforza, Duke of Milan, and sister-in-law to the King of France. She was one of the most powerful women of the period.

Even before the work was finished, a number of illustrated pages were stolen from Birago's workshop, a disaster the artist lamented in a letter that briefly came to light in Italy in the 19th century.

Birago blamed a friar who visited his studio for the theft of 12 pictures and 13 pages of text showing the calendar and 16 other images. He valued the total stolen at around 500 ducats - what one expert said yesterday was five times the cost of Leonardo da Vinci's Virgin of the Rocks altarpiece in the Louvre, made at about the same time.

Bona of Savoy used the book, which contained devotional texts, just as it was left by the theft. But when Margaret of Austria, regent of the Netherlands and Bona's niece by marriage, inherited the manuscript, she had the missing leaves replaced by her own court painter, Gerard Horenbout, a famous Flemish painter. Thus the book, considered one of the three best treasures in the British Library's collection of 10,000 such manuscripts, remained.

The first evidence the missing leaves still existed came to light in 1941, when a page illustrating the Adoration of the Magi was discovered and presented to the library. In 1984, another, depicting the month of May, came to light and was purchased from a New York dealer. And it later emerged that the dealer had kept another, showing the month of October, for himself.

Years passed and that dealer became ill. The library's experts made anxious inquiries as to the whereabouts of his collection, eager to claim the October leaf for their own. But when they discovered it was now in the hands of another dealer in Chicago, he gave them just one month to raise £191,000.