France's national library has bought the memoirs of celebrated Venetian lover Giacomo Casanova, which were initially thought to have perished at the end of World War Two.

The 3,700 fading yellow pages of Casanova's "Histoire de ma Vie" (Story of my Life) were discovered packed in a dozen boxes which had been transferred to a safe just days before the allied bombing of Germany in 1945.

"During the Second World War Leipzig was bombed, but the boxes were discovered in the basement of the bank where they were being kept. They were in good shape," Marie-Laure Prevost, curator of Bibliotheque Nationale de France, told Reuters TV.

"Everyone at that time was touched when this manuscript was found. Even Churchill asked whether it survived the bombing," added Prevost.

France's national library paid around seven million euros for the memoirs, which Casanova started writing while working as a librarian in 1789.

"The Casanova manuscripts are the most important purchase ever made by the library ... And of course it is a great event from a cultural and heritage point of view," said Bruno Racine, head of the library.

Casanova describes his amorous adventures in the script, which he modified continually until his death in 1798.

"It is one of the most published texts in the world with hundreds and hundreds of publications and ... they have always been corrected, simplified, falsified. So what is important for us is to find the authentic truth," added Racine.

The purchase was funded by a private donor and the library hopes to exhibit the manuscript in autumn 2011.