To staff at the British Library, the well-dressed Iranian gentleman was a regular and well-respected visitor to the private reading room where he studied valuable ancient texts.

Several times a month for six years Farhad Hakimzadeh, 60, would take out six books at a time, mostly dating from the 16th and 17th century, and sit alone, quietly poring over their pages.

A respected author of books on Europeans from the period travelling to the Middle East, and a millionaire with his own vaunted book collection, he aroused no suspicion.

Closed-circuit television cameras and plainclothes guards patrolling the reading room never detected his true purpose. But, instead of reading the library’s rare and precious books for pleasure or research, he was carefully cutting out pages to add to his own collection “with the precision of a surgeon”.

Hakimzadeh, who is director of the Iran Heritage Foundation, also stole rare pages from books in the collection of the Bodleian Library in Oxford.

A library spokesman said: “We cannot put a price on these books — they are invaluable.”

A civil claim against Hakimzadeh is being pursued by the British Library for the recovery of pages taken from another 150 books, or for compensation. The total cost of the damage that he inflicted on books from the British Library could be up to £1 million — one map alone that he cut out of a book was worth £30,000.

Experts believe that he was either replacing damaged pages in his own collection or adding pages and illustrations that the original owners of the hand-made books had ordered to be specially prepared for their editions.

After carefully cutting out the pages, with a scalpel or a razor, he would either have them professionally bound into his own books, enhancing their value, or insert them loosely.

Hakimzadeh will be sentenced today at Wood Green Crown Court after admitting 14 charges of theft at an earlier hearing.

Although four specimen charges were brought involving books from the Bodleian’s collection, a spokesman said that since 2003 he had taken pages from another 47 volumes.

Two complete books that he had taken from the Eastern Art Library, also in Oxford, were recovered.

Dr Kristian Jensen, Head of British and Early Printed Collections at the British Library, described his actions as “targeted mutilation” and “an attack on the nation’s collective memory of its own past”.

When police searched Hakimzadeh’s home in Knightsbridge, London, they found on display in his library 14 examples of his destruction, ten from the British Library and four from the Bodleian.

Dr Jensen said: “These thefts have struck at the heart of the British Library’s historic collections making their loss and the vandalism that accompanied their theft especially harmful. He is an author with a profound knowledge in this field and that makes it worse because he knew the importance of what he was damaging.”

The alarm was raised when a reader at the British Library took out one of the books damaged by Hakimzadeh. Staff checked to see who was recorded as having taken it out and when. Once they narrowed it down to him they began an exhaustive exercise to check each page in more than 1,000 books.

Experts were able to match one of the pages found at Hakimzadeh’s home to a book in the British Library as it had exactly the same mark made by a book worm. He was charged in September last year after a lengthy investigation and claimed initially to have bought the suspect books at a second-hand market.

Hakimzadeh was born in Iran and studied in America, receiving degrees from the Massachusetts Institute of Technology and Harvard Business School. The London-based businessman has an American passport and a home in Houston, Texas, according to documents filed at Companies House.

Last year he resigned his directorship of IB Taurus, an independent publisher with offices in New York and London.

One source involved in the investigation told The Times: “We will never know the full range of his motivation. It is such an unusual thing to do, which is why it was so hard to detect.”

Dr Jensen said that Hakimzadeh had betrayed the trust of the library. “The violation of the collections transcends mere monetary loss. His victims are the researchers of the future who will not be able to consult this material.”

Texts vandalised by Hakimzadeh

Some of the books damaged at the British Library:

Geschichte der schöhnen Redekünste Persiens, mit einer Blüthenlese aus zweyhundert persischen Dichtern Author: Hammer-Purgstall, Joseph, Freiherr von, 1774-1856, date: 1818

Historia oriental de las peregrinaciones de F. M. P. Author: Mendes Pinto, Fernando, 1620

Une Ambassade extraordinaire. La Perse en 1839-1840. Avec . . . un avant-propos du Comte Laurent de Sercey Author: Sercey, Félin Édouard de, Count, 1928

De Paris à Samarkand. Le Ferghanah, le Kouldja, et la Sibèrie occidentale Author: Bourdon, Marie Ujfalvyne, 1880

Istoria de la China i Cristiana empresa hecha en ella Author: Ricci, Matteo. Jesuit, 1621

Breue relacion, de la peregrinacionque ha hecho de la mayor parte del mundo Author: Cubero, Sebastian Pedro, 1688

J. G. W’s Ost-Indian – und Persianische Reisen Author: Worm, Johann Gottlieb, 1745

Mithridates Author: Lee, Nathaniel, 1693

Novus orbis regionum ac insularum veteribus incognitarum Author: Grynaeus, Simon. Professor of Greek at Basle, 1537

Historia della Persia Author: Pasta, Giovanni, 1650

From the Bodleian Library:

The travels of Mirza Abu Taleb Khan . . . Abu Talib Khan, translated by Charles Stewart (London, 1810)

The embassy of Sir Thomas Roe to the court of the great Mogul William Foster, (London, 1899)

Notes on some early Persian lustre vases Henry Wallis, (London, 1885) from the Eastern Art Library, now part of the Sackler Library

Godman collection of oriental and Spanish pottery (London, 1901) also from the Eastern Art Library