You have been allowed to handle one of the world's oldest and most precious books - and as you turn the pages, you notice with horror that the paper is starting to crinkle under your finger.
For such fragile manuscripts, crinkles are but a step away from cracks and tears.
This frisson of nightmare has to date been available only to a few privileged scholars permitted to touch the books, but from today can be shared by all the 10 million UK households that are online.
The British Library has put 10 of its greatest and rarest literary treasures, from the Lindisfarne Gospels to the world's earliest dated printed book, the Diamond Sutra, on to the internet.
Tony Blair yesterday hailed the project, Turning the Pages, as a "magnificent example" of what the internet could achieve.
The electronic facsimiles are so realistic that the pages do appear to crinkle as they are turned by mouse clicks. However, the damage is an illusion. Smaller details, almost invisible on the actual manuscripts, like the realistic cat on the opening page of the Lindisfarne Gospel of St Luke, are revealed by a zoom facility.
The zoom also shows the glee on the faces of the devils and lascivious women who torment St Anthony in a play ing-card sized painting in the Sforza Hours, a book of hours commissioned by the Duchess of Sforza in the 1490s.
The painting, by Giovan Pietro Birago, was once so celebrated that it was insured for more than Leonardo da Vinci's Madonna of the Rocks. Today, Leonardo's notebook of drawings and writing is probably the most valuable item of all the collection.
Most of the digitised versions have been readable on terminals for about 100,000 visitors to the library's exhibition galleries in its headquarters near St Pancas station in London. The prime minister, who has visited the galleries' set-up, said in a tribute to the spreading of the page-turning technology to the internet that it "opens access to a broad spectrum of our cultural heritage".
Other books on the website are the Luttrell Psalter (1590), the 14th century Hebrew Golden Haggadah from Spain, the Sherborne Missal of around 1400, Sultan Baybars' Koran of 1306, Elizabeth Blackwell's Herbal of 1737-1739, and Andreas Vesalius's Anatomy from the 16th century.
To see Turning the Pages, go to bl.uk/collectionstreasures/digitisation.html/. The site requires a Macromedia Shockwave plug-in, which can easily be downloaded.
